2.2.2. Conscientiousness

Conscientiousness was assessed using a 12-item scale selected from the shortened Chinese version of the NEO Five-Factor Inventory (NEO-FFI) [43]. All items (e.g., "I try to be the best at anything I do") were rated on a 5-point Likert scale, ranging from 1 (*strongly disagree*) to 5 (*strongly agree*). This scale showed good reliability and validity in the Chinese sample [44]. In the present study, Cronbach's alphas for conscientiousness were 0.84 at T1 and 0.87 at T2.

#### 2.2.3. Positive and Negative Affect

Emotional well-being was evaluated using the Positive and Negative Affect Schedule (PANAS) [45], which is a self-rated measure of positive affect (PA) and negative affect

(NA). Huang et al. [46] have verified that the PANAS is appropriate for use with Chinese populations, and shows good reliability and validity. The scale consists of 10 affective adjectives for PA (e.g., "attentive", "excited", and "inspired") and 10 affective adjectives for NA (e.g., "ashamed", "guilty", and "irritable"). Each participant rated how they felt in general from 1 (*very slightly or not at all*) to 5 (*extremely*). Cronbach's alpha coefficients were 0.85 for PA at T1, 0.84 for NA at T1, 0.86 for PA at T2, and 0.87 for NA at T2.

#### 2.2.4. Life Satisfaction

The Satisfaction with Life Scale (SWLS) [47] is widely used to assess the cognitive component of subjective well-being. The standardized Chinese version of the SWLS was adopted in the present study [48]. Respondents were asked to indicate the degree to which each item was true for them on the 5-item scale (e.g., "in most ways, my life is close to ideal") from 1 (*disagree strongly*) to 7 (*agree strongly*). Cronbach's alphas for the scale were 0.90 at T1 and 0.89 at T2.

## 2.2.5. Physical Symptoms

The Cohen–Hoberman Inventory of Physical Symptoms (CHIPS) [49,50] was designed to assess general physical symptoms. The Chinese version of the CHIPS was proved to have good reliability and validity in the Chinese sample [51]. This scale comprises a list of 33 common symptoms (e.g., "acne", "back pain", and "heart pounding or racing"). Respondents were required to rate "how much that problem has bothered or distressed you during the past 2 weeks?" on a 5-point Likert scale ranging from 0 (*not been bothered by the problem*) to 4 (*extremely bothered by the problem*), with higher total scores indicating lower levels of physical well-being. Cronbach's alphas in this study were good in the two waves (T1: α = 0.94; T2: α = 0.93).

#### *2.3. Data Analytical Strategies*

Descriptive analysis and partial correlation analysis were conducted on the key variables at T1 and T2. Paired *t* tests were then performed to detect differences in these key variables between the two waves. Finally, a set of cross-lagged regression analyses were adopted to assess the reciprocal relationship between conscientiousness and well-being. All statistical analyses were conducted using IBM SPSS Statistics 25.0.

#### *2.4. Assessment of Common Method Biases*

Since all study variables utilized self-rating measures, a Harman single factor test was employed to assess the common method bias [52]. A total of 70 items from the questionnaires at T1 were subjected to the exploratory factor analysis without rotation. The analysis produced 17 common factors, with the first explaining the 19.17% variance, and the analysis of 70 items at T2 yielded 17 factors, with the first explaining the 19.40% variance, both of which were lower than the critical standard of 40% [53]. The results indicated that the correlation between the studied variables in this study was not driven purely by method bias.
