I'm not an aggressive person at all, although back in high school I had a bad month where this was not always the case.
My senior year, I had a boyfriend I was pretty crazy about...and one day he just seemed different. Held me at arms length, didn't invite me to his house after school (which had been a daily ritual of ours). I knew immediately something was wrong, and by the end of the day he had dumped me in the hall by the band room.
I didn't really know how to handle what I felt after that. I was the "new kid" in school, and this guy had pretty much become my touchstone. I no longer knew who to sit with at lunch, what to do after school, who to talk to...where his friends really still my friends, now that we were broken up? I internalized all this, and eventually it started to bubble to the surface.
One day at drama class, some nerdy freshman was being a jerk. Playfully teasing me. I pushed him into a pile of folding chairs and they flew everywhere. He wasn't hurt, and everyone laughed. That same day, I punched a friend of mine in the shoulder. I had meant it as a joke, but I did it a little too hard. I remember thinking this isn't like me. I tried to calm down.
The next day at lunchtime, I went to sit with a "friend" who I'll call Angela. I use the term "friend" loosely: she was condescending, on medication that made her delusional, a bit of a faker for attention, and only friendly with me when it suited her. Our friendship had been a bit forced, due to the fact we lived nearby and our parents saved money by carpooling us. She was a perky preppy with a boyfriend on a hockey team, I was a sullen goth who had just been dumped by the star of the drama club. We couldn't have been more different, and after a few months of this forced friendship, the strain was beginning to show.
At lunch, she made me "sit with her" even though there was no room available at her table. So I had to kneel at her feet. Like a dog. Considering she already ordered me around, this probably just felt appropriate to her. Sometimes a seat would clear up at a nearby table and I would try to take it, and she would whine and pout at me until I returned to sitting near her.
After probably weeks of kneeling like a dog (at least one day a week, because we had alternating lunch blocks), it finally dawned on me that this all had placed Angela in a power position...and she was relishing it. This day in particular, she had taken her apple and banged it on the table until the apple had exploded all over her hand.
"Ew," she said. "Apple guts!" And she wiped her hand on my shoulder.
In a split second, my brain decided that I couldn't take any more of this girl, and I gave her a shove. I don't remember how hard it was--if it was actually hard enough to hurt her, or if she was faking--but she fell off her chair and landed on the floor.
The table of guys--all friends of Angela's, no one I really knew--looked at me, horrified and angry. My stomach sank at the realization that not only had I hurt her, but now I'd have to deal with them, too.
She got up crying and went immediately to the nurse. The table full of guys stared at me. I stared back. I can imagine I was white as a sheet.
Then, as soon as Angela was out of earshot, they all broke into applause and smiles. Some of them clapped me on the back. I was confused.
"Good for you," one told me.
"We were all wondering how much longer you'd put up with her," said another.
Later I found out that her elbow had been broken. She came in the next day with her arm in a sling, on medication that made her even loopier than before. She apologized for wiping apple guts on me, I apologized for pushing her, and we barely spoke again after that.
There was another time, years before this...where I gave a boy a well-justified black eye, right in front of the school principal. But that's a story for another day...