Beat the Element of surprise by awareness, analysis of the possibilities, and proactive reaction or even instinctive reaction when possible. You should be aware of the threat and know your response time limits. Be aware of any possible opponent using the element of surprise and possibly having an in-sight or concealed knife.
Avoid anything that causes distraction which will slow down your action. After you analyzed the potential danger in your immediate surroundings, pay attention to the speed, angle of approach and body positioning angle as he is approaching the hotzone. That means that if your opponent is talking to you , do not talk back as it slows your brain from executing a prompt reaction.
React proactively if you can. That means that you either avoid getting to close, or turn the tables and attack your opponent first. Your mind could be rehearsing your move before you execute it if you have the time on the conscience level or subconsciously. Keep the correct sequence of desired unfolding of the event, and the execution of desired technique.
Remember the knife is just an extension used by a more capable destructive opponent. You must eliminate your opponent's capability to react within a split second in order to secure your safety!
While you learnt to deflect and counter attack moves, you must drill enough and know that in feinting scenarios, your desire is to attack according to the distance. If you were thinking that the attacker was coming from a certain direction charging the blade from a certain direction, your brain made a plan how to deflect and hit him before it was too late to do so.
Finally, remember attacks scenarios can unfold slowly or very quickly. You cannot afford to think too much as the attacker is getting near the hotzone. As he gets closer, slow down your thinking and speed up on your action. You must not hesitate and be very decisive. Especially if you see a blade, don't slow down trying to spare his life, before you control the situation ensuring you are staying alive.
Bare Hands vs. Knife Video Clip