To your point shaggy.
I know of two different reactions to the fight responce.
the out of control one you are describing.
hands usually drop or reach for the opponant
chin pointing up in the air.
This is a natural reactionalong with mouth slightly agape teeth showing.
That is all bad news.
Through hard sparring and fighting you have to change that reaction to something practical.
Hard to do when you are pissed. REPETITION is the only way.
When you feel that feeling it should be your clue to resist nature.
chin down, shoulders shrugged, elbows protecting the mid section. Turn sideways to make a smaller target bla bla bla.
Once you get hit in the jaw with a few hooks while your mouth is agape you will learn.
of course the swelling will not allow your mouth yo shut correctly for a week or so.
So yeah nature must be overridden in this case unless you like being beat up.
When you are angry.
overconfident or tired is when you are most likley to go primal and have your jaw wired shut.
good day