" Self-control is an exhaustible resource. This is a crucial realization, because when we talk about “self-control,” we don’t mean the narrow sense of the word, as in the willpower needed to fight vice (smokes, cookies, alcohol). We’re talking about a broader kind of self-supervision. Think of the way your mind works when you’re giving negative feedback to an employee, or assembling a new bookshelf, or learning a new dance. You are careful and deliberate with your words or movements. It feels like there’s a supervisor on duty. That’s self-control, too. "

― Chip Heath , Switch: How to Change Things When Change Is Hard