I joined the thread a little late and I didn't read much posts but I'll say this: martial arts fights aren't like the ones in the street. I'm not saying martial arts doesn't help, it helps A LOT, but most people assume that the attacker is just going to stand there and take everything you can throw at him. Also, the worst assumption is that the attacker won't fight dirty.
It's real life, you are going to fight dirty in every street fight. Yeah, it's dirty fighting but who the fuck cares if you don't feel like bashing each other repeatedly like gentlemen? Still, there is one thing I hate: Kicking someone while they are on the ground. There is a reason why kicking someone who is on the ground is probably the most hated dirty fighting move. He is down already and he isn't going to hurt you. If you are still kicking, that's not you defending yourself.
Also, who draws first blood is at a gigantic advantage. If you get hit first, you'll be less confident and it will show, you'll be stunned (if the first hit was strong enough) and you'll probably won't be able to counter or evade the second hit. We never expect it to happen, but it happens. You'll get punched when you don't expect it. So, if the argument is getting worse you better be ready for it. Also, don't forget that the first person who delivers the first strike will be the WRONG guy (and you will be the BADASS guy if you counter a first strike) and if there are some helpful people around, they will try to get him down, not you. However, it's not going to matter a lot if you are in a dark alley with no witnesses.
In our fantasy land, we are all badasses with our invented fighting moves and shit. Chances are, you'll probably forget your every fantasy about you beating your boss/your rivals/Justin Bieber with awesome moves when you get into a fight. You might turn into a hopeless slapping machine or simply run away. Even if you try to execute a move, you might forget about the fact that what you are fighting is a human, and he will definitely react to your every move.
To cut it short, if you are not ready for the psychology of a fight, you'll probably get your ass kicked. This is from personal experience. I got sucker punched so hard once, I literally ate away a part of my cheek (I still have scars in my mouth) and my left ear was deaf for 2 months. Psychology is your most important weapon in a street fight. My friend faked mafia affiliation once to get someone off his back. If you are successful with the psychology part of a fight, you might even win without fighting. I'm tall and big but I usually give a Gentle Giant and Nice Guy impression (no, I'm not gonna give TvTropes links. I'm not a monster) and this is a weakness for some people. Once I have realized this, I have learned to use swear words well and fake attitudes, like acting a crazy psychopath. It never works when it's someone who knows you well enough to see through your mask but if it's a stranger you can get him to shit his pants and have him running scared, or you can possibly get him to want to kick your ass more. I think it's something important as martial arts knowledge, but it doesn't help much when the REAL fighting (not just pushing or slapping each other) is occurring.