There's a natural instinct embedded in friendship, a sympathy that makes us willing to fight for someone we like when they are treated unjustly.

As people strengthened their willpower muscles in one part of their lives—in the gym, or a money management program—that strength spilled over into what they ate or how hard they worked. Once willpower became stronger, it touched everything.

There’s something really powerful about groups and shared experiences. People might be skeptical about their ability to change if they’re by themselves, but a group will convince them to suspend disbelief. A community creates belief.

At some point, if you're changing a really deep-seated behavior, you're going to have a moment of weakness.

This is the real power of habit: the insight that your habits are what you choose them to be.

The cooperation of NASCAR - or any other system, it turns out - persists only when everyone believes he has the opportunity to win.

Willpower isn’t just a skill. It’s a muscle, like the muscles in your arms or legs, and it gets tired as it works harder, so there’s less power left over for other things.