reincarnation
a. what if, after you die, you live again?
b. what if you were a famous person in the distant past?
c. what if the life you're living now is the life you deserve for your past actions?
d. what if the life you're living now is the life you'd wished for as an improvement on your past circumstances?

These are options but they're also in order of decreasing commonality. I think (d) is the most interesting because it comes with the question: what kind of wish was that, and why would it be made? And trying to answer that question might put you in a perspective to appreciate your life.