If you could go back in time just once...

[Whispers]

If you could go back in time just once to do, or undo, anything, where/when would you go and what would you do? =o

I'd go back to when I was about 10 or 11 and live my life completely differently than I have. I'd like to say I'd prevent something like 9/11, but how could I do that? They completely ignored the threats that preceded it, I doubt a guy claiming to be from the future would deter them any further. =p