Emerging evidence suggests that individuals who spontaneously engage in self-affirmation—by reflecting on their personal strengths, values, or social relationships—tend to demonstrate greater psychological resilience and well-being in the face of everyday psychological threats. Despite growing interest in this construct, the mechanisms through which spontaneous self-affirmation contributes to adaptive outcomes remain underexamined. This study draws on theoretical perspectives that emphasize self-adequacy as a key mechanism underlying the beneficial effects of self-affirmation. We propose that spontaneous self-affirmation enhances psychological adjustment by strengthening individuals' beliefs in their ability to manage life demands effectively. To test this hypothesis, we designed a two-wave longitudinal study. In the first wave, conducted in early October 2025, 385 participants completed self-report measures assessing spontaneous self-affirmation, general self-efficacy, and psychological adjustment. Cross-sectional analyses of the first-wave data supported our expectations that spontaneous self-affirmation was positively associated with self-efficacy, which, in turn, was positively associated with higher psychological adjustment. Furthermore, self-efficacy mediated the relationship between spontaneous self-affirmation and psychological adjustment. Although these preliminary findings are cross-sectional, they point to the proposed indirect effect through self-efficacy. The second wave, to be collected in early January 2026, will provide a stronger longitudinal test of these pathways using structural equation modeling. Together, the findings suggest that spontaneous self-affirmation may serve as an individual resource that promotes psychological adjustment through enhanced self-efficacy.