It's one thing to own and shoot a gun on the range. It's another thing to use it to shoot another human up close and personal, with little or no anticipation of self-recrimination oi legal after-effects.
Take George Zimmerman, for instance --
You are exactly right. I don’t know of any way to prepare for that. The only thing I know to do is spend as much time as possible on the range getting comfortable with it until it’s second nature.
As you pointed out, if the time came, you’d have plenty of other things going on in your mind without worrying about the mechanics.