1. Introduction
Psychological well-being is one of the topics of positive psychology that has received a lot of attention from researchers in recent years [1]. It is considered as a necessity of life including good mental health, high life satisfaction, a sense of meaning or knowing the purpose, and the ability to manage stress [2, 3, 4]. Psychological well-being is often thought of as a combination of positive emotional states such as happiness (hedonistic perspective) and performance with desirable effectiveness in individual and social life [5]. Psychological well-being refers to the meaning, purpose, and satisfaction of a person’s life [6]. Researchers have emphasized the importance of psychological well-being in protecting against inflammation and reducing the risk of developing viruses [7]. At the individual level, it has been conclusively shown that impaired psychological well-being may have a detrimental effect on health, but positive psychological well-being may play a protective role in health [8]. Studies show that there are several factors associated with psychological well-being, two of which are mentioned.
A sense of gratitude has always been of interest to scholars, and all major religions have emphasized loyalty to gratitude, especially to God [9]. Gratitude shows how grateful people are for what they have in life, knowing that they have not been given it forever [10]. High levels of gratitude can have various benefits in different areas of life such as social welfare, mental health, physical health as well as mental and psychological well-being [11]. Research shows that gratitude is of the most beneficial positive personality traits [12] and is the mother of all virtues [13]. Some experts believe that gratitude can increase psychological well-being and work conflict [14]. Grateful people tend to experience fewer negative emotions such as jealousy, depression, and resentment [15]. Gratitude has one of the strongest links with well-being and life satisfaction, even compared to other positive virtues, such as optimism or compassion [16]. A study found that 38.4% of gratitude contributed to well-being [17]. 
Numerous studies with different groups have shown that the practice of appreciation increases the feeling of energy, alertness, vitality, success in achieving personal goals, better coping with stress, feeling more purposeful and flexible, strong and secure social relationships, strengthened sense of worth and confidence, and generosity and helpfulness [16]. The results also showed that gratitude is related to psychological well-being, and grateful people are happier, healthier, more lovely, better able to cope with stress, more humble, less narcissistic, more forgiving, and more spiritual [18]. In one study, participants were asked to write a weekly thank-you note for three weeks. At the end of the exercise, the results showed that they were happier, less depressed, and more satisfied with their lives [19]. In this regard, psychological interventions showed appreciation that is associated with increased happiness, mental well-being, and reduced depressive symptoms one month after the intervention [20]. Studies showed that psychological well-being and the meaning of life can be enhanced through gratitude interventions [21]. Similarly, gratitude interventions were able to increase the rate of gratitude [22, 23]. Numerous new studies have shown that there is a relationship between gratitude and psychological well-being [24, 25, 26].
Optimism is one of the variables related to psychological well-being (the tendency for good experiences to occur in life), defined as a relatively stable personality trait that determines the type of behavior of a person with an optimistic direction about the future, evaluates stressful situations and situations that endanger psychological well-being with a positive outlook (having generalized expectations for positive outcomes), and uses these abilities to overcome problems [27]. Optimism, which is a general approach and orientation about life, means paying attention to the positive things in life and not dealing with the negative aspects of it. Optimism means looking forward to positive events in the future and a kind of cognitive structure that usually leads to motivation to strive [28]. In the same context, optimism helps a person to achieve more success in life, the work environment, and other areas of life than others’ expectations. 
Optimism activates the immune system, which makes a person less likely to develop infectious diseases and see a doctor less often. Optimists tend to view the causes of negative events as transient, situational, and external. Optimism is associated with psychological benefits such as less anxiety, mental well-being, life satisfaction, positive emotions, resilience, less depression and hopelessness, and a problem-oriented active acting style [29]. Optimism is a lasting trait when it relates to different contexts and affects psychological well-being [30]. Some experts believe that both optimism and resilience are major elements of psychological well-being [31]. Studies have shown that hope and optimism have a positive relationship with psychological well-being [32, 33]. In this regard, the results of several studies showed that there is a relationship between optimism and psychological well-being [34, 35, 36, 37, 38, 39, 40]. 
Given that the recent challenge posed by COVID-19 is related to psychological well-being [41], and consequently the physical and mental health aspects of students such as anxiety [42], distress [43], and lack of participation in learning activities [44] have changed their lifestyle and academic life [28], the government, educators, and psychologists needs to maintain or promote psychological well-being [45]. Since psychological well-being has been considered by experts, we can pay attention to important protective issues such as appreciation and optimism, because gratitude and optimism help increase the psychological well-being of individuals [46]. On the other hand, empirical research has shown that high levels of gratitude are associated with mental well-being, life expectancy, hope, optimism, empathy, and expressing gratitude with positive emotions and increased social motivation [47]. In this regard, the results of studies show that increasing gratitude and compassion can help improve mental health and reduce the effects of stress and fear of COVID-19 to positively affect mental health [48]. 
To protect the psychological well-being of people, which is a source of their health, it is very important to pay attention to the mentioned issues. That is, due to the prevalence of COVID-19 disease, the physical and mental health of people, especially students, affected by this disease, and the need to face the effects of this disease led to the identification of protective factors against this disease in this study. In other words, the present study shows that during the outbreak of COVID-19, psychological well-being can be maintained through optimism and gratitude. On the other hand, since studies have shown that COVID-19 affected all aspects of human life, especially educational issues, to maintain academic motivation and improve psychological well-being, important and effective variables should be identified. Therefore, identifying such variables can minimize the vulnerability of individuals. This study investigated the role of protective factors (optimism and gratitude) in the psychological well-being of students.

2. Methods
Participants
The present research design is correlational. All male and female students in the fields of psychology, educational sciences, and counseling at Payame Noor University in Khuzestan province included the statistical population. Due to the prevalence of coronavirus and lack of face-to-face access to students and by designing a WhatsApp link, 393 people (301 girls and 92 boys) were selected voluntarily. The higher number of female students in this study is rooted in their choice of Payame Noor University and their priority to the city of residence. On the other hand, the number of female students is higher than male students, and also the priority of many boys is to find a job and have an income rather than study. 
To conduct the present study, the implementation and distribution of questionnaires were approved by the education department of the Payame Noor University of Ahvaz. In other words, because the present study was conducted during the COVID-19 outbreak and the classes were held virtually and direct access to the above students was not possible, 393 people were selected voluntarily. Male and female students of educational sciences, psychology, and counseling at the Payame Noor University of Khuzestan Province and satisfaction with participating in the research were the criteria for entering the study. Not completing the questionnaires and not specifying the gender on behalf of the subjects were the criteria for leaving this research. Questionnaires were distributed and collected through a WhatsApp link. It should be noted that the present study was conducted during the outbreak of COVID-19. 

Research tools
The following questionnaires were used to measure the research variables:
Psychological well-being questionnaire: To measure psychological well-being, the 11-item psychological well-being questionnaire by Sevari [49] based on Tennant et al. [50] was used. The questionnaire is scored on a five-point Likert scale from strongly agree (5) to strongly disagree (1). The reliability of the items was assessed by Cronbach’s alpha of 0.80 and its validity was confirmed by confirmatory factor analysis. In the present study, the reliability of this questionnaire was obtained at 0.87 through Cronbach alpha. Its validity was verified through confirmatory factor analysis (IFI=0.91, RMSEA=0.06).
Gratitude questionnaire: Gratitude was measured by Sevari’s Questionnaire [51] obtained from 200 students of Payame Noor University of Ahvaz through exploratory factor analysis. The questionnaire consists of 3 items. Cronbach alpha reliability of all female questionnaires was 0.90. The validity of the questionnaire was confirmed through confirmatory factor analysis. The scoring method is based on a four-point Likert scale from strongly disagree (1 point) to strongly agree (4 points). The questionnaire’s validity was verified through confirmatory factor analysis (IFI=0.93, RMSEA=0.07).
Optimism questionnaire: Optimism was measured by Sevari’s questionnaire [52] based on Millstein et al’s questionnaire (2019). The questionnaire consists of 7 items scored on a 5-point Likert scale from strongly disagree (1) to strongly agree (5). Its reliability was 0.74. Its validity was verified through confirmatory factor analysis (IFI=0.90, RMSEA=0.06).
Descriptive statistics (Mean±SD) and inferential statistics (Pearson correlation and multivariate regression) were used to analyze the data. The Kolmogorov-Smirnov test was used to check the normality of the data. Data analyses were conducted via SPSS software, version 27.

3. Results
Table 1 shows that female students (n=301, 77%) and male students (n=92, 23%) have the highest frequency and percentage, respectively. The Mean±SD of students’ age was 22.42±2.52. Table 1 shows the demographic characteristics of the subjects.

Table 2 presents the Mean±SD and normality test of the data related to the research variables. Table 2 shows that the Mean±SD for the psychological well-being variable of female students is 38.79±10.07 and 38.90±10.06 for male students.

The Mean±SD for the variable of optimism of female students is 25.59±6.33 and 23.84±7.28 for male students. The Mean±SD of the gratitude variable of female students is 10.29±2.45 and 9.80±2.69 for male students The results also show that the mean score of female students in optimism and gratitude is higher than boys’ while the mean score of psychological well-being of male students is higher than girls’. In addition, the findings of the Kolmogorov-Smirnov test indicated that the data distribution was normal.
Table 3 presents the findings related to the correlation between the variables.

Table 3 shows that there is a significant positive correlation between optimism and psychological well-being (r=0.61, P=0.03) and between gratitude and psychological well-being (r=0.55, P=0.001). 
Table 4 presents the findings of predicting psychological well-being through optimism and gratitude.

Stepwise multiple regression analysis showed that optimism alone explains and predicts 37% of psychological well-being and the combination of optimism and gratitude predicts 42% of psychological well-being. Based on the results, the third hypothesis of the research is confirmed.

4. Discussion
As mentioned earlier, in the present study, the protective factors of students’ psychological well-being during the corona outbreak were studied. In this regard, the results showed that there is a significant positive relationship between optimism and the psychological well-being of students. The results of this research are consistent with the results of Werdani [34], Garvin & AdhiPutri [35], Sánchez-Aragónm [36], Duy and Yildiz [37], Parveen et al. [38], Datu and Mateo [39], and Nguyen & Le [48]. The results of the study by Sabiq and Miftahuddin [53] showed that optimism is related to well-being. Chang and McBride [54] stated that optimism is related to positive results desired by a person such as good moral conditions, satisfying achievement, and the ability to solve problems that had been arisen. Optimism is a style of explanation and a positive mindset for the future when individuals think about the causes of an experience [55]. 
Explaining this finding, the optimism as a stable trait affects psychological well-being [30] and as a relatively stable personality trait determines the type of behavior. Optimism gives individuals an optimistic outlook on the future and positively evaluates stressful situations and situations that endanger their psychological well-being [27]. In other words, optimism helps a person to be more successful in life, work environment, and other areas of life and goes beyond others’ expectations. In this regard, some believe that optimistic people tend to evaluate the causes of negative events as transient, situational, and external. Optimism is also associated with less anxiety, higher mental well-being, higher life satisfaction, positive emotions, resilience, less depression and hopelessness, and a problem-oriented active style of acting [29]. Optimism leads people to find beliefs that empower them to make positive assessments of the social context and environment, and therefore expect positive results. In other words, confirming the results of this study, it has been observed that optimistic people have high mental and physical health and life satisfaction due to having a high sense of well-being and positive emotions, and positive evaluation of events around them [56]. It can also be said that optimism makes a person have a strong expectation that everything will be fine despite the obstacles and discouragements in life as a whole. 
Some experts believe that both optimism and resilience are major elements of psychological well-being. It is necessary to mention that optimism is defined as a generalization of expectations that good results occur in all important areas of life. The results of a study by Strassle et al. showed that life is associated with psychological well-being, physical and mental health, and fewer mental disorders [57]. Optimism not only motivates action but also rewards behaviors that function adaptively. Optimists consider obstacles, failures, and unfortunate events to be temporary, situational, and external.
The results of the present study also showed that there is a significant positive relationship between gratitude and psychological well-being. The results of this research are in line with the results of Portocarrero et al. [25] and Yildirim et al. [26], Atad and Russo-Netzer [58], and Farzadi et al. [59]. Explaining this finding, grateful people are happier, healthier, more lovable, better able to cope with stress, more humble, less narcissistic, more forgiving, and more spiritual [18]. In this regard, it must be said experiences indicate that adolescents with more gratitude report more optimism, positive emotions, and more satisfaction with school life. 
The psychological nature of gratitude has important implications for social functioning and individuals’ well-being. Gratitude, as a positive emotional state, also increases a person’s resilience and tolerance in life and helps his well-being. In addition, gratitude helps students to form and maintain communication in college to have more social communication. It can provide them with social support. As a result, such people in stressful situations will have less confusion and distress and they will experience higher well-being at university. It is worth mentioning that gratitude occurs when individuals perceive that they have obtained an intentional benefit from another person or a higher being [47]. 
Gratitude is an other-oriented emotion since people tend to feel grateful precisely when they receive a benefit provided by another person [54]. In part, gratitude is an emotion that occurs after people receive aid that is perceived as costly, valuable, and altruistic [60]. On this basis, several researchers have conceptualized gratitude as an emotion that is always directed toward appreciating the helpful actions of other people [61]. In one study, participants were asked to write a weekly thank-you note for three weeks. At the end of the exercise, the results showed that they were happier, less depressed, and more satisfied with their lives [19]. In this regard, psychological interventions showed that gratitude is associated with increased happiness, mental well-being, and reduced depressive symptoms one month after the intervention [20]. Czyzowska and Gurba [21] showed that psychological well-being and the meaning of life can be enhanced through gratitude interventions. Similarly, gratitude interventions were able to increase the rate of gratitude. Educators and parents must use valid experimental methods and interventions to increase college welfare for students to thrive in gratitude conditions. For example, students can be asked to participate in gratitude interventions such as counting blessings.

5. Conclusion
The results showed that girls’ mean score of optimism and gratitude is higher than boys’ mean score, while the psychological well-being of boys is higher than that of girls. The results showed that there is a significant positive relationship between optimism and gratitude with psychological well-being and 42% of psychological well-being can be explained and predicted through optimism and gratitude. Deletion of some questionnaires due to incomplete answers to questions and lack of face-to-face access to students due to the prevalence of COVID-19 were among the limitations of the present study. It is suggested that those in charge of education try to increase students’ optimism as well as gratitude through training courses, which will help improve their psychological well-being.

Ethical Considerations
Compliance with ethical guidelines
This study has been approved by the specialized research group of psychology and educational sciences of the Payame Noor University of Khuzestan. (Code: IR.KHZ.PNU.1401.1). All ethical principles were considered in this article. The participants were informed about the purpose of the research and its implementation stages. They were also assured about the confidentiality of their information and were free to leave the study whenever they wished and if desired, the research results would be available to them.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
All authors equally contributed to preparing this article.

Conflict of interest
The authors declare no conflicts of interest.


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