There are so many good books on the psychology of self defense.

Regardless of the tool (weapon), it all boils down to the same thing:

Can I convince the bad guy that I will hurt or kill him?

If that requires brandishing, well...that's what you do. No warning shots or other nonsense. You have to make your attacker believe you'll put a bullet in his brain box if he persists. If you can't do that with a hot pink .25 auto, you're not going to suddenly be able to do it with a .44 Magnum snub loaded with flying ashtray JHPs.

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Psalm 27:2