Research on employee perfectionism and its duality is shifting from a mere dispositional perspective to consider the state-like nature of this phenomenon. Despite recent findings identifying negative work experiences as antecedents of daily perfectionism, the role of positive experiences remains to be elaborated. Bridging the principles of trait activation and stress-as-offense-to-self theory, the present study examined the role of daily appreciation as a positive, self-affirming experience for the expression of daily perfectionistic cognitions at work and its implications for well-being (vigor, serenity) beyond the workday. We expected that the impulse of daily appreciation would carry over into vigor and serenity at bedtime and at the beginning of the next workday by triggering daily perfectionistic strivings and serving as a protective factor against daily perfectionistic concerns. Data from 170 employees who participated in a daily diary study over two consecutive working weeks were analyzed using multilevel mediation analyses (multilevel structural equation modeling). In support of our hypotheses and the idea of a butterfly effect, daily appreciation was indirectly related to serenity at bedtime and to vigor and serenity at the beginning of the next workday via daily perfectionistic cognitions. We discuss implications for supervisors and organizations and encourage scholars and practitioners alike not to underestimate the role of positive self-affirming experiences and personality dynamics at work. (PsycInfo Database Record (c) 2024 APA, all rights reserved).