By the way, I look on my brief flirtation with bodily harm as a high point in my school career 
Well, maybe not a high point, but, I’m not as sorry as I should be I think.
I was 13-14yrs old. I am the last person you’d ever imagine would raise a hand to anyone in anger.
It was me having tolerated years of low level bullying from this boy and his brother, and friends. Me and my sister both. That year, my sister had became very ill, in fact terminally ill, except for this amazing experimental operation, which gave her approximately a 40% chance. And it turned out that operation was sheer butchery. And afterwards, she had to wear this foul cast over most of her body. For a year. That gave her sores, infections, she smelt, but the worst thing was that it was a few inches thick, and formed with no thought to the shape of a teenage girl.
So, when that awful boy just said one sentence to her, on that first day back, just one tiny jeer about her body, I lost it completely. I remember screaming at him and I punched him as hard as I could in the stomach.
He was completely taken aback, and actually apologised. I still remember him saying ‘I didn’t know, I didn’t know...’ waving his hands at me to make me stop.
Which was a shame as I’d was very much up for more of a fight. I really, really wanted to hurt someone, badly. I reluctantly believed him, for some reason I don’t think he did know about my darling sisters operation. (Probably hiding in his bedroom being a typical teenage boy, missed all the local gossip!).
I remember feeling really bloody angry that this meant I couldn’t hit him again. Which was a shame at the time.
No one reported it, so nothing happened, except I think I was gossip for a week. And the boy got ribbed for being hit by a girl. The quietest girl in school who never said anything back to teasing or bullying. But no one teased my sister about that sodding cast. Which is probably another reason I don’t feel that ashamed about my behaviour. Which is a cop out really isn’t it?
Really, I could have written that incident up so differently.
I could have slid quietly over my reasons, my state of mind, me protecting my sister. And I could have jumped to me wanting to hurt him so much, me coming at him totally out of the blue.
In a way, he just happened to be there, saying the one thing that I could excuse my behaviour for. I could let myself off the hook and punch the hell out of him, the convenient stooge for all the pain and powerlessness I’d felt all that year.
Not so nice really was it? 
And if you throw in his broken home and horrible father etc, then it could sound very different indeed.
Oh and definitely miss out that I’m a complete wuss who left absolutely no damage whatsoever (I didn’t even wind him, not even cause him to get a little breathless. Depressingly bad at it really! I’d make an extremely bad bodyguard or bouncer!).
Anyway, my point being, that facts are that you, like me, didn’t do any lasting damage, and you, like me, have some excuse that you could use.
So long ago, it becomes about your perspective and how you tell it to yourself. You could have told yourself you snapped and the bully deserved it, that you were a victim not really the aggressor.
I think the way you tell the story to yourself, well, it makes you a very good person. Or a person carrying around disproportionate guilt and shame for an incident that happened a very long time ago.
Maybe a bit of both?