For the past few decades, psychological researchers have been aware of a phenomenon called ego depletion: the wearing down of willpower and self-control. The most common understanding of the subject holds that willpower is a finite resource, which can be used up or exhausted over the course of a single day (Baumeister et al, 1998). This has been supported by research showing that when a person is asked to exert a ton of willpower (for example, by ignoring loud noises to complete a difficult task), they make more impulsive decisions afterward.
