Your mistake was not in imagining things you could not know—that is, after all, what imagination is for. Rather, your mistake was in unthinkingly treating what you imagined as though it were an accurate representation of the facts.

Everyone who has observed human behavior for more than thirty continuous seconds seems to have noticed that people are strongly, perhaps even primarily, perhaps even single-mindedly, motivated to feel happy.

Lower your cortisol level. The happiest people have the lowest level of cortisol, a stress hormone that raises blood pressure and weakens the immune system. Cut the stress-more yoga, less road rage-and you'll cut your cortisol production.

Psychologists call this habituation, economists call it declining marginal utility, and the rest of us call it marriage.

Most of us appear to believe that we are more athletic, intelligent, organized, ethical, logical, interesting, open-minded, and healthy-not to mention more attractive-than the average person.

Your mistake was not in imagining things you could not know—that is, after all, what imagination is for. Rather, your mistake was in unthinkingly treating what you imagined as though it were an accurate representation of the facts.

Variety improves the things that we do too often, but it rules the things that we don't do often enough.