Everybody does something stupid eventually, and has something that wasn't their proudest moment ever.
It might be sad and painful now, but as life moves on, so do you. For me, school wasn't a very happy time, and I've had much better times since, as well as times that could rival the bad times I had lol.
I no longer talk to the friends I made at school and uni - we just sort of drifted apart, which kinda goes to show how much life can change (and it didn't take long for that to happen lol).
Focus more on your future than your past - what happened, happened, so you can't change it now, but you can change where you're headed.