There is a pale scar on my arm from where a blade sliced me open in high school.
It was not self-harm, though it was arguably self-inflicted or at least a result of a stupid decision. This is what happens when you give a group of high school drama students access to swords that are not exactly approved for stage combat.
I don't remember the exact assignment other than it was related to choreography. It started as trying to figure out how to come up with a short dance number, but quickly got sidetracked into "Let's try blocking out a fight scene." Swords were obtained (from who or how I also cannot remember) and a group of fledgling drama students with no training and too many hours in front of movie and tv screens got to work.
I stood at one end of the stage and my opponent -- a boy named Simon -- stood at the other. We waited for our cue and then rushed each other. The swords were metal and dull, so we thought them safe. Simon brought the sword down slowly and I parried. We worked through a scene where he got to hold the sword to my throat and I broke away by kicking him and doing a roll across the stage. We thought we were being careful.
We were not.
I brought my arm up to block an oncoming blow and a moment later I felt something wet on my skin.
"Oh my God! Are you okay?"
I glanced down and saw blood trailing down my arm. It didn't hurt that much so I shrugged, lowering my own sword now. "It's just a scratch."
Of course our teacher did NOT see it that way. She insisted we go back to class and patch it up. I left my sword and accepted the brown paper towel someone offered me. Staunching blood with the cheap paper towels they keep in high school bathrooms does not work as well as you might think. It does not replace a band-aid, no matter how much your dumb high school brain may insist it does. I cannot recommend it for first aid purposes.
That's how you end up with scars that last into your 30s