I got KO'd by myself once. It was during school P.E, and me and some friends were pretending we were doing dunks on a pullup bar. There just happened to be a leak above the ceiling, and there was no caution sign. I tried doing a 360, and landed straight on the back of my head. I don't remember much that time cause I just walked home and went to sleep for the rest of the day. Next day I was ok.