things go bad and you make mistakes you can't take back?
I'll say age 9. Probably the last good year before a boy starts liking girls, and that's where things start spiralling out of control in a bad way. Because shit just gets fucked up with girls on the brain.
When you're 8, you're a king. You know how fast you are, how strong you are...you're not clumsy anymore in your body. You're pretty good at your sports. You have your buddies, and you know where the best BMX trails are, where the good fishing spots are, how to punch a kid hard enough the nose to leave you alone (and no one pulls a gun). You can kill a squirrel with a slingshot and all your buddies think that's pretty cool. You have a bunch of friends...not so many, but not too few.
Yep...age 9 was sweet.
Then age 10, I had a crush on Lynn. Things did not go well for me after that. I still haven't figured out women and my brain seems unlikely to give up worrying about women.