Absolutely nothing. Nothing at all. Except Jesus did say:
"He said to them, 'But now if you have a purse, take it, and also a bag; and if you don't have a sword, sell your cloak and buy one.'" Luke 22:36
So see, Jesus approves of self-defense. An no, "turn the other cheek" was not referring to pacifism and letting people hit you, so let's put that to rest right now.