A somewhat depressing lesson that we learn from life is that there is no guaranteed sure-fire formula for happiness.
MICHAEL W. EYSENCK, Happiness: Facts and Myths
We have all had the experience of being happy and of being unhappy, and we have all observed happiness and unhappiness in other people. As a result, many people feel they are experts on the topic of happiness. This claimed expertise, however, is often illusory. There is a natural tendency for us to assume that what is true of our lives is generally true of other people's lives. Thus, if someone has discovered that he is happier in the married state than he was when he was single, he may conclude that marriage increases human happiness. On the other hand, someone whose level of happiness has gone down after marriage may well decide that marriage is an outmoded happiness-demolishing institution. The fallacy in attempting to draw general conclusions solely on the basis of one's own experience is obvious.