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.

The pleasant life: a life that successfully pursues the positive emotions about the present, past, and future.

Optimism is a tool with a certain clear set of benefits: it fights depression, it promotes achievement and produces better health.

Habits of pessimism lead to depression, wither achievement, and undermine physical health. The good news is that pessimism can be unlearned, and that with its removal depression, underachievement, and poor health can be alleviated.

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.

I'm trying to broaden the scope of positive psychology well beyond the smiley face. Happiness is just one-fifth of what human beings choose to do.

Well-being cannot exist just in your own head. Well-being is a combination of feeling good as well as actually having meaning, good relationships and accomplishment.