Suppose you could go back in time to any point in your life and re-live it from then on. When would you go back to and what would you (try to) change? What if it was just to re-live certain parts of your life differently and then jump back to the present day? Would it be different in the second scenario?
Tell me what you would change, and when I get time I'll come back and tell you why you're stupid.
(I would reject the opportunity to go back in time. Feel free to tell me why I'm stupid.)