It is just a case of letting the adrenaline take over, IE: having a knife stuck in my arm late last year it felt more like a burning across the entire area than actual pain, I looked at it, looked at the person who put it in me, looked back at it, then pulled it out, apparently the look on my face was enough to convince him to leave...
As soon as he was off and down the street, I proceeded to swear profusely, writhe in pain a little bit then headed off to my desk, where I keep (no joke) a medikit, sterilised the wound and taped/bandaged it up
That knife now resides on my desk, a little reminder of what people can do when you accidentally sleep with their girlfriends...
One thing worth noting is, for me, big injuries, (punches, kicks, knives, elbows and skateboards to the face) have less of a pain oriented effect on me than stubbing my toe or biting my tongue, THOSE injuries have me running around my house screaming "Orrthuckthukthurcktharrtfuthinghurtslikeshit!" Do you guys find that? or is it that I am a natural victim to clumsiness, yet a stalwart survivor of physical attacks?