When do you face a challenge? How unnecessary tasks block the challenging potential of time pressure and emotional demands.

Job demands push employees to invest energy in certain behaviors to perform well, which can come with both costs and benefits to employees' well-being and motivation. Previous research presents contradictory results concerning whether specific job demands are a challenge (i.e., motivating) or a hindrance (i.e., only distressing). Building on the conservation of resources theory and the success resource model, we propose achievement experiences as an important work-related resource and indicator of whether job demands are challenging or hindering. We hypothesized that time pressure and emotional demands are positively related to achievement experiences (task-related and prosocial), contingent on the perception of unnecessary tasks, which in turn relate to work engagement and emotional exhaustion. Weekly diary data were gathered from 323 employees over the course of 4 weeks. Multilevel moderated mediation analyses revealed that time pressure and emotional demands unfold their challenging potential when unnecessary tasks are less frequent, and that these effects hold true for matching demands and achievement experiences (task-related and interpersonal dimensions). Overall, our study provides a resource-based theoretical rationale for the ambiguous results reported by various other studies, and it emphasizes the importance of subjective achievement experiences for employees' well-being. (PsycINFO Database Record (c) 2019 APA, all rights reserved).