Abstract: Individual work performance fluctuates considerably within persons across days and even hours, yet traditional performance models focus primarily on stable between-person differences. This article synthesizes recent research demonstrating that momentary affective states substantially influence episodic work performance through their impact on attentional resource allocation. Drawing on affective events theory and the episodic performance framework developed by Weiss and colleagues, we examine how negative emotional states misallocate attention away from task demands, impairing concurrent performance, while certain positive affective states can enhance attentional focus. We distinguish between background core affect and discrete emotion episodes, showing that emotion episodes—characterized by heightened arousal, cognitive elaboration, and regulatory demands—exert particularly strong effects on attention and subsequent depletion. The article integrates evidence from experience-sampling studies across diverse occupations and discusses organizational implications for performance management, work design, and employee wellbeing. Practitioners gain insight into managing the affective climate of work, designing tasks with appropriate attentional pull, and recognizing that daily performance variability represents meaningful psychological processes rather than mere measurement error.