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.

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.

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.

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.

I believe that traditional wisdom is incomplete. A composer can have all the talent of Mozart and a passionate desire to succeed, but if he believes he cannot compose music, he will come to nothing. He will not try hard enough. He will give up too soon when the elusive right melody takes too long to materialize.

Positive thinking is the notion that if you think good thoughts, things will work out well. Optimism is the feeling of thinking things will be well and be hopeful.

Success requires persistence, the ability to not give up in the face of failure. I believe that optimistic explanatory style is the key to persistence.