Research has shown that individuals' stress mindset—the belief that stress is enhancing or debilitating—can be altered through interventions. However, the daily fluctuations of stress mindset and its interplays with psychological outcomes in natural context remain underexplored. This study aimed to investigate the dynamic characteristics of positive and negative stress mindset in daily life, as well as its reciprocal effects with psychological well-being. 356 college students completed their stress mindset and psychological well-being measures for seven consecutive days (five assessments per day). We examined the dynamic characteristics of the internal system of positive and negative stress mindset, as well as their interplay with psychological well-being. Dynamic structural equation modeling found that positive stress mindset was significantly weakened by negative stress mindset. More importantly, the self-perpetuating loop between negative stress mindset and negative affective experience further diminished positive stress mindset. These findings highlight the dynamic nature of stress mindset, pinpointing the susceptibility of positive stress mindset to daily negative influences, as such call for targeted interventions on protecting and cultivating a positive view of stress.