Treo
Bullet Proof
If the guy has no weapon other than his bare hands, you are likely looking at jail time for manslaughter. Legally "grievous bodily harm" is not a reasonable expectation from a bare handed attack. It is a possibility, but not a reasonable expectation sufficient to warrant deadly force. This not my opinion, but a paraphrase of one of the most popular texts on criminal law.
Like I said I can only assume you've never been in a real fight. IE one in which the other guy is trying to kill you.
As I asked before, while you are down there on the ground how are you going to stop me from literally jumping both feet on to your chest (crushed rib cage) or kicking your head like a foot ball?
This isn't high school homeboy, do you really want to trust the good intentions of a random criminal who is pissed off enough at you to knock you to the ground?
I can't help you overcome the mental block in your head but I promise you in the real world if you get knocked to the ground in a fight ( again, why are you engaged in fisticuffs in the first place?) you are in real danger.