Think of your willpower as a muscle that gets tired with use. You may push yourself to get the report done at work, push yourself to choose salad over pizza at lunch, and then push yourself to call ...

Answer by Dan Ariely, Professor of Psychology and Behavioral Economics at Duke University, on Quora: One of the main things that people don’t understand about motivation is the pleasure principle.

I write a lot about motivation, because finding long-lasting motivation to exercise is perhaps the most important part of your exercise journey. You can find lasting motivation in your self-identity, ...