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.

Companies aren’t families. They’re battlefields in a civil war.

The same process that makes AA so effective—the power of a group to teach individuals how to believe—happens whenever people come together to help one another change. Belief is easier when it occurs within a community.

I think I'm smart, and I know I was a good mom. But there wasn't a lot I could point to and say, that's why I'm special.

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

Shampoo doesn’t have to foam, but we add foaming chemicals because people expect it each time they wash their hair. Same thing with laundry detergent. And toothpaste—now every company adds sodium laureth sulfate to make toothpaste foam more. There’s no cleaning benefit, but people feel better when there’s a bunch of suds around their mouth. Once the customer starts expecting that foam, the habit starts growing.

Typically, people who exercise start eating better and becoming more productive at work. They smoke less and show more patience with colleagues and family. They use their credit cards less frequently and say they feel less stressed. It's not completely clear why. But for many people, exercise is a keystone habit that triggers widespread change.