You should learn foot to ground combat. You can't stop a knife with your hands. You're just going to get stabbed or shot because putting yourself closer to a knife or deadly weapon is willfully throwing away remaining luck. All true defense is improvisation, because if you knew anything ahead of time, an offensive strategy would be sought. If it is determined that a preemptive strike cannot be obtained, the result by some is defense through paranoia—which could be what you're doing depending on the context. Improvisation cannot be taught, but running away can be the go-to plan for even the slowest at choosing a reaction. The only other thing is to remember to bluff without hesitation should avoidance options be limited. Anything can happen in these situations. Can someone teach you to pick up a chair, rock, pocket sand, garbage can, a drink, your ex girlfriend, used baby diapers, HIV+ blood, or whatever and throw it to escape? If you can't do a random thing on demand now—like blowing and spitting your onion breath in assailant's face—how will anyone teach it to you?
Carry a loaded gun or move to a better neighborhood. It's better than LARPing as an action movie martial artist.