"Things happen fast. When the worst happens, we fall back on our training."
That's what my CHL instructor drilled into us. He was a DEA agent in South America for 25 years, and has been in more than his share of gunfights. He says that under the crushing, heart-stopping, breath-stopping, paralyzing stress of a face to face gunfight, you will NOT think about "the right shot to make" or "the right thing to do." What you will do is follow your training, whatever that may be.
For many police officers, their "training" means standing in an indoor range, slowly drawing the pistol, clicking off the safety, firing a shot into center mass, and reholstering. And in a real gunfight, that's what they'll do, and they will die.
Or miss. And miss, and miss, and miss, and miss. I read a story once of 4 street cops who opened fire at a crazed gunman at a range of 15 feet, emptying their semiautos. The bad guy killed two of them. Not a single one of their shots hit the target? Why? They were following their training: draw, safety off, fire, reholster.
Decide what your instant, non-thinking response will be to a close range gun encounter. E.g., a double fail (two quick unaimed shots to center mass, an aimed shot to the head), or acquire the front sight, or whistle the National Anthem backwards, or whatever you like.
Then practice it over and over until you can instantly draw and perform it instantly, in a blur, without thinking. In front of you, to your left, to your right, behind you, while sitting down, while lying face down on ground, while walking different directions, and so on, until it is as natural as breathing.
Because whatever you do in your training, that's what you'll do when the lead's coming your way.