" Dieters have a fixed target in mind for their maximum daily calories, and when they exceed it for some unexpected reason, such as being given a pair of large milkshakes in an experiment, they regard their diet as blown for the day. That day is therefore mentally classified as a failure, regardless of what else happens. Virtue cannot resume until tomorrow. "

― Roy F. Baumeister , Willpower: Rediscovering the Greatest Human Strength