Once a depressed person becomes active and hopeful, self-esteem always improves. Bolstering self-esteem without changing hopelessness, without changing passivity, accomplishes nothing.

Optimism is invaluable for the meaningful life. With a firm belief in a positive future, you can throw yourself into the service of that which is larger than you are.

In your own life, you should take particular care with endings, for their color will forever tinge your memory of the entire relationship and your willingness to reenter it.

Positive emotion can be about the past, the present, or the future. The positive emotions about the future include optimism, hope, faith, and trust. Those about the present include joy, ecstasy, calm, zest, ebullience, pleasure, and (most importantly) flow; these emotions are what most people usually mean when they casually-but much too narrowly-talk about "happiness." The positive emotions about the past include satisfaction, contentment, fulfillment, pride, and serenity.

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.

Some find that very optimistic people have benign illusions about themselves. These people may think they have more control, or more skill, than they actually do. Others have found that optimistic people have a good handle on reality. The jury is still out.

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