Train getting hit.
In some karate they put you in a corner and some tough bb punches your body and after a while it teaches you to take it (and the bb goes harder and faster). One tenses, moves, lets it slip etc. I imagine that learning similar head movement would take a lot of the force out of the strike.
If you like pain, get someone to slap you, over and over and practice moving your head with the direction of the blow.
Or you could get a neck like this guy and just break people's hands:
its not that i can't handle it, i'm still not used to it. cool keeping the jaw tight makes sense. basically there is nothing i an but, take hits. thanks thats cleared that up.