Someone taking a swing at you is not a your life or theirs situation. My reaction to violence will be measured by the violence used against me. Taking a swing will get you knocked out, pulling a knife will put me in a position to where I must finish you before you can me. If that requires me to kill the attacker then I am prepared for that. May sound like Macho crap, but I don't care. I train for combat. I train to survive violence through violence
I'm going to expand on my earlier comments a bit.
I have always made it a point to tell students that it is much easier to hurt someone a lot, than to hurt them a little. And harder still to subdue them without injury.
Perhaps you've not reached a point in your training where anything other than the most brutal response is an option. If that is the case, I withdraw my comments about macho ********. If that is the case, then it's just a matter of training.