I got angry a few times and kind of snapped at my best friend. I'm sure I did it with others, but I remember those times with her the clearest. I felt terrible even the second after it happened. I was so enraged that I couldn't accomplish something and she was good at it. But then I felt so mortified after hurting her (unintentionally) that I wanted to cry and disappear. Once I tried to clear her head with a high karate kick (like I'd seen in a movie) and I hit her in the temple and bent her glasses. The other time I swung a golf club super hard at a miniature golf course and the ball shot into her leg (I was so pissed that I had missed like 3 times having the ball come right back to me). I think the third time was her beating me at some game and me flipping the board...so just a tantrum. She was good at everything. It got to be annoying, but now I see I was just an emotional beast and didn't realize how much I was affected by my chemistry. Doesn't make me feel better about what I did, but now that I know what's going on and I'm a little older, at least I can challenge the invasive and explosive emotions. I also used to storm off if I felt wronged by a teacher or whomever. I had a terrible time with authority figures...esp the ones who used their power with a bit too much relish.
You're not alone.