... that's what my Jesuit mentor used to say. Now it seems to be the subject of major scientific inquiry. See Favored by the Gods. (Hat tip, Dave Lull.)
Naturally, the new Calvinism declares that, with regard to happiness, as with regard to everything else, we are genetically predestined.
For what it's worth, experience has led me to conclude that happiness is not something that happens to you, but something that you can work at and achieve. Meaning, after all, as Abraham Maslow noted, is intentional.