my 2 crashes from this past season went like this.
1) loside at about 90mph....had some front brake and was turning it in when the front just went. i think i hit a patch on the track where it is slicker than the rest of the track, but i dunno. next thing i know im sliding along through the grass and im thinking, fuck. then i slide over a bump and my head hits the ground as a result and then my thoughts arent so clear.
2) hiside at 110....goin into a corner off a straight, downshift and the fucker didnt stay in gear, popped a false neutral and then back into a gear quicker than you know what. as a result the abck end locked up and started hopping, 2 hops and it grabbed, went to the side, came back adn threw me off. next thing i know im looking down at my gas tank which is eve with my feet thinking this is gonna hurt a lot. next memory is being on my feet walking towards one of the pieces of my bike.
so as for crashing...my advice is similar to jeffs, relax and dont try to move. thinking oh shit this is gonna hurt a lot helps in my case. other than that, just remember thats why you paid $500 for your helmet and who knows for your suit, boots, gloves etc.....that why you buy good gear.