Harvard Professor Daniel Gilbert has written a book called Stumbling on Happiness. Here are some exerpts from the article:
"our decisions about what will make us happy -- or unhappy -- almost always are clouded by inaccurate memories and over-reliance on present feelings."
"you can't rely on your past or present to predict your future because brains file away only a few cues to memory, mainly the highs and lows of an experience."
"Ignorance about the brain's defenses against unhappiness also distorts judgment"
"people of every age and every walk of life seem to regret NOT having done things much more than they regret things they did."
Since we assume in economics that people try to maximize their utility or happiness, this seems like an important book. Although he may be right that we don't always know what will make us happy, if we make mistakes, it does not mean we are not rational. Remember, to be irrational means we intentionally make ourselves worse off. So if you don't do the right thing to make yourself happier because you didn't know what it was, you are not necessarily irrational.