Happiness is a Function of Personal Predictability

If you are so unpredictable that you even you cannot predict your future self, then it is unlikely you'll be happy. Happiness is a function of personal predictability -- you need to know a lot about your future self.

If you can predict what your future self will enjoy, it is easier to be happy. But if you buy a pink BMW now and your future self hates it ... That might be a problem.