I did boxing for couple of years, and still do. And I have had fights on street as well.
Yeah, all MMA top fighters have background in BJJ and whatnot. But then again, you must remember that MMA and most other fighting sports are, well a sport.
Lying on the ground during a street-fight, is a fucked up situation to be in. You never know when a buddy of his can "sucker kick" you in the head.
On the street nobody will stand infront of you, and wait while another guy announces that the fight has started. The agressor will always use his advantages over you (dark street, jumping from behind, sucker punch, using a weapon, etc). When you respond to an agressor, you're fighting on his terms, not yours. There is no "ring", there are no points, no refs, nothing. Just you and the agressor, fighting on his terms. If you have the chance to run, then just motherfuckin run. If you're with a GF or other person that might get hurt because of you fleeing, or your life is in danger, well that's another story, and be my guest to break that fucker's skull.
You must also remember, if you go to court for giving too much damage, understand that street fighting and self defence are two different animals. Self defence means that you have to get out of the "clusterfuck" situation as fast as possible. Kick in the balls and run - that is self defence.
Kneeing the "enemy" after you have punched him 3 times in the face and solar plexus is street fighting. I don't know how it is in US or any other country - you must look at laws, or speak to a lawyer about that. But yeah - don't mix streetfighting and self-defence those are two different things. And if you did "too much" of self-defence, you can be classified as the agressor, even if the guy pushed you first.
Oh, and, well atleast in my country, if you use the term "self defence" to cops or in court, you just basically screwed yourself. Because when you mention "self defence", you are now in a position where you have to proove yourself that it was justified to use force to defend yourself. It is a very tight line between self defence and street-fighting.
Be careful when you do that.
And all the talk about "BJJ vs Boxing", etc. It doesn't matter that much. It mostly depends on the person. You can't say Thai-box is better than kickbox because you saw a thai-boxer knocked out a kickboxer. It depends on the person.
My two cents - ANY training will help. You just have learn to cope with "fight or flight" response. Also when you're training, you mostly don't get the "real" adrenaline rush that you get on the street, and adrenaline rush is a real bitch. Get some training, and learn to keep your mind as calm as possible.
BTW, why Jap samurais samurais where so fucking cool? One of their keys was that they were able to keep calm during the whole clusterfuck that was happing in the battle.
Learn to control yourself, know when someone is provocating you, and use your brain more often than fists.
Almost all streetfights start because someone hurt someone's ego. Of course, real attacks happen (thugs, robbers and such), but you can avoid almost all fights if you don't fuck over someone's ego, and stay calm when someone else calls you a "pussy". You got to learn to recognize that. Don't allow the ego to take over your common sense.
Been there, done that.
Shiiiittttt.... this was a long one.