When it comes to our health, there are essentially four things under our control: the decision not to smoke, a commitment to exercise, the quality of our diet, and our level of optimism. And optimism is at least as beneficial as the others.

Ten years ago, when I was on an airplane and I introduced myself to my seatmate, and told them [I was a psychologist], they'd move away from me. ... And now when I tell people what I do, they move toward me.

On the relationship side, if you teach people to respond actively and constructively when someone they care about has a victory, it increases love and friendship and decreases the probability of depression.

In a society in which individualism is becoming rampant, people more and more believe that they are the center of the world. Such a belief system makes individual failure almost inconsolable.

The pursuit of happiness is enshrined in the Declaration of Independence as a right of all Americans, as well as on the self-improvement shelves of every American bookstore. Yet the scientific evidence makes it seem unlikely that you can change your level of happiness in any sustainable way. It suggests that we each have a fixed range for happiness just as we do for weight. And just as dieters almost always regain the weight they lose, sad people don't become lastingly happy, and happy people don't become lastingly sad.

People who believe they cause good things tend to like themselves better than people who believe good things come from other people or circumstances.

Changing the destructive things you say to yourself when you experience the setbacks that life deals all of us is the central skill of optimism.