We rarely ask and even more rarely answer that question honestly. We need to ask ourselves what ought to make us happy, and answer accordingly. Indeed we need to ask ourselves what exactly we mean by happiness first. I've been very happy lately with my golf game. But it is a fleeting, vain happiness, if I am to be honest with myself. In fact, it's downright shallow.
Socrates, that old pagan, famously opined that the unexamined life is not worth living. Aristotle taught that happiness is the highest goal, and that the greatest happiness comes from examination of the greatest things. Aquinas expanded on that further by saying that the greatest happiness comes from thinking about God. And I think I'll leave it at that.