I know I am prepared to deal with someone high on drugs and someone drunk, because I have done it! I have had two self defence situations the first on was a drunk guy (two but I had a friend), the second was with a guy who had been sniffing glue and paint (don't know if this is a stimulant or depressant). I don't think I will every need to deal with a mugger as they target easy weak people. I do, however, feel confident from my two encounters and training that I could defend my self against an untrained person. If I did not I would not train at a self defence school.
You missed my point. And yes even big strong guys like you do get mugged or worse. I don't think its something you can be too confident about. Self defense Is about common sense and luck.