"There are certain kinds of work that require immersion into the task before progress can begin. In this category I include jobs like writing, research, analysis, invention, and programming. The immersion time is required to overcome a kind of mental inertia. ... When highly immersive tasks are interrupted, a second immersion period is required to get going again. There may also be a frustration component if interruption is frequent." Slack: Getting Past Burnout by Tom DeMarco