I seem to have taken the thread off on a tangent here with my guilty admission so apologies. The only point was that as someone with very little skill, and not even meaning to hurt anyone, I had the unfortunate experience of possibly ending someone's career with a kick to the knee.
As to the several people who messaged me privately to help assuage my sense of guilt, thank you. The guilt comes from having caused serious and possibly life-changing bodily harm to someone who may not have even really hurt me. All they wanted was my money. Did they really deserve to have their knee destroyed?
It also had to have been somewhat humiliating for a high school brawny guy like him to have to admit to his family and friends that some scrawny little new kid in town took him out so quickly and heartlessly walk away from it without even really thinking about it or even putting much effort.
Anyway, back on topic, the point is even a relative rookie could hurt someone with some essential defensive training. To become consistently adept though, I'd still standby my original statement that it'd take a few years. Just my $0.02