I used to have a boyfriend who started to self harm when we were together. He would bang his wrists of a surface for ages and end up with bruises, like really big black painful looking ones, eventually he moved onto cutting amongst other things.
No matter how I tried I couldn't understand why he would want to do this to himself, even when he tried to explain why he felt the need to do it, and got so frustated. It was soul destroying to watch someone you love hurt themselves, and have no explanation other than it feels good.
One night I lost my honeysuckle after I found him harming, I threw a kitchen knife at him and told him to do it properly. Not proud of that moment, i remember thinking "f**k, what have i just done!!!!!". I think that was due to my lack of understanding. After that i made it my business to look it up and try to understand, so i didn't do something so shitty again, i was horrified at my actions.
We're still friends, and he's a lot better now, moved on, married with a baby girl. guess that was something he had to go through at that time, he says he regrets his actions and the scars he's left with, as he says its his souviners from a long hard journey.
I don't pretend to know why people do it, i don't like it, but who am I to say what you can and cant do with your body, i would say channel your emotions into something less harmful, but it would fall on deaf ears if your gonna do it, your gonna do, at the very least be safe about what your gonna do, it's only common sense.
(That was a load of my chest, jeezo)