In many jobs, employees must manage multiple projects or tasks at the same time. A typical workday often entails switching between several work activities, including projects, tasks, and meetings. This paper explores how such work design affects individual performance by focusing on the challenge of switching attention from one task to another. As revealed by two experiments, people need to stop thinking about one task in order to fully transition their attention and perform well on another. Yet, results indicate it is difficult for people to transition their attention away from an unfinished task and their subsequent task performance suffers. Being able to finish one task before switching to another is, however, not enough to enable effective task transitions. Time pressure while finishing a prior task is needed to disengage from the first task and thus move to the next task and it contributes to higher performance on the next task.