Self Defense/Grab and stab
How do you deal with a "Folsom Prison" style attack, where the attacker grabs you with one hand and stabs you with the other? Assuming everything's gone wrong and he's got his hand on you and his knife out, what do you focus on? Do you try to free yourself from the grab, or do you concentrate on the weapon?
Most often you die.
This especially because the legit-version of this strategy is usually done by two attackers, one grabs and holds, the other stabs. If the guy knows what he is doing he is going to stab you repeatedly in the worst possible area to get shanked. While you can often survive multiple stab wounds, if the guy knows where to hit, you're screwed. This is a professional hit and the best protection is
a) stay out of prison
b) have a prison crew to protect you
c) do NOT piss of dangerous people.
The wanna-be version (or blitz) that is being shown out there as 'a real knife' attack I have serious problems with. Fundamentally it only works if the target does the absolutely most stupid thing there is to do. Yet if you, the target, do that, it outrageously effective.
The problem is people default to the stupid.
They especially do so because often what is happening is a monkey dance (See Rory Miller's Meditations on Violence). When we are in a monkey dance and are -surprise surprise -- attacked by an attack we provoked, then we respond in this default manner.
If the guy has a knife in his hand you get the shit cut out of you.
The problem with your question is -- until you learn how to break the default response -- you're going to get carved.
But the answer, I give you will not work until you can break the default.
You'll think you understand what I am saying, but your default will keep you doing the stupidest things possible. Things that will only get you stabbed again and again. Straight up the kinda killer commando combatives, deadly RBSD crap out there -- that shows you to jump in there and beat the hell out of him -- IS THAT stupid default.
Until you break that default, that is what you are going to try to do. You'll misinterpret and will not be able do the following advice.
Get off line/behind his elbow
Twist his head off
Slam it into the ground
That's the physical aspect, functionally it is very easy to do. What is hard to do (and what I spend entire weekends training people) is overcoming the default reactions that are going to get you trying to 'fight' the guy.