Well, this is a bit tricky. Considering that a change at the age of 11 might make me not know how it ends up at 27, so I can't change something then, you only really have the ability to make a major change once. After that, your life will be different, so you might not end up being in the later situations.
Changing a situation is a bit tricky. The first thing that comes to mind is stopping playing tennis at the age of 11, as I caught an illness and me continuing playing tennis made me get a long time illness that semi-incapacitated me for the entire rest of the period.
On the other hand, that illness made me who I am today. If I hadn't faced that, I would most likely have become an overconfident, oversucessful person who had never met any real trouble in life. I could quite easily have become an arse.
Essentially, there's nothing little enough for me to worry about it now, and all the bad stuff is stuff that happened to me, not stuff I did. If I changed it, I would also change, and I'm perfectly happy with the current me.
I wouldn't really change anything.
