not to be argumentative (what? who, moi?), but i've known a guy who got stabbed, ran after the guy and, well, did him no favours. i've also known a guy to be hit on top of the head with a piece of bundled cable and not find it the least bit amusing. granted, these are exceptions, but it's possible.
i'd add that kicks to the crotch doesn't instantly bring a guy down (not that i remember, anyway). it takes a moment or two: you swallow your balls and that's when the inconvenient ache sets in, and by 'inconvenient ache' i mean dehibilitating agony along the lines of 'oh, god, kill me now and spare me this torture!'
as mentioned, you *will* get cut in a knife fight. accept it before getting in one. (well, that's what the book said, at least.)
most people aren't in as good shape as they think they are. i know that after a slight workout my eyes are ready to shoot from my sockets.
all it takes is one good punch to not want any more/be unable to respond. so don't take that high road and wait for the attack: if you're in a fight, get the first punch in.
you are not the ultimate fighting champion. avoid fighting if you can. hang out in a bar long enough and you'll find plenty of amusement in the form of fisticuffs eventually. honestly, a lot of these guys i think get in fights to impress idiot girlfriends with the idea that they'll be broken up (the fight, not the couple, because most habitual bar brawlers don't have that much good sense) before gawdawful damage happens. then again, like i said, one good punch... a guy i know once punched an idiot square in the face, sending him into emergency reconstructive surgery. one punch. (later that night, my buddy's house was broken into and ransacked, his cousin visiting the place was beaten up.)