Drawing from the affect theory of social exchange (Lawler, 2001) and regulatory focus theory (Higgins, 1997, 2012), we examine when and how challenge and hindrance stressors representing favorable and unfavorable social exchanges between employees and the organization, respectively, relate to interpersonal helping and deviance. Based on three-week, twice-daily experience sampling data from 78 employees, our results show that challenge stressors contribute to “emotional uplifts”—upshift in positive affect (PA) coupled with downshift in negative affect (NA), whereas hindrance stressors contribute to “emotional downs”—downshift in PA and upshift in NA for employees with a stronger prevention focus. Moreover, a prevention focus accentuates both the direct relation of hindrance stressors with PA downshift—NA upshift and the indirect relation of hindrance stressors with interpersonal deviance through PA downshift—NA upshift. Specifically, on days when employees are confronted with hindrance stressors, those with a higher prevention focus tend to experience stronger PA downshift—NA upshift, and subsequently enact more deviant behaviors toward coworkers. Importantly, we examined the mediating role of affective shift over and above established mediating mechanisms (affect levels and stressor appraisals). We discuss the implications of our findings for theory and practices.