“This effect, which is named for the experimental work of the early-twentieth-century psychologist Bluma Zeigarnik, describes the ability of incomplete tasks to dominate our attention. It tells us that if you simply stop whatever you are doing at five p.m. and declare, “I’m done with work until tomorrow,” you’ll likely struggle to keep your mind clear of professional issues, as the many obligations left unresolved in your mind will, as in Bluma Zeigarnik’s experiments, keep battling for your attention throughout the evening (a battle that they’ll often win).”