Six rules

Maybe you have seen the silly viral video of "Man With Concealed Carry Permit Arrested For Exposure Of Gun" ... if you haven't, perhaps you will ... it's almost a guarantee that you will see it if you are involved in law enforcement or law enforcement training. This cop and this motorist are BOTH really lucky to be alive ... change the circumstances ever so slightly and this doesn't turn out so well [for either one] ... BOTH made severe mistakes, both made careless assumption about the other.

The video reminds me of MY "rules" for thinking about these kinds of deadly force situations:

1. When you carry a weapon, EVERY confrontation that you get involved in is an ARMED confrontation. Somewhere, out there, there is someone who can take your gun away from you and use it against you. Just because it hasn't happened yet, don't expect your ridiculously good luck to continue. See rule #6.
2. Unless you have good reason to actually KNOW otherwise, you have to assume that everyone you meet might be ARMED. Some of the people who are armed are actually dangerous. Nothing is more dangerous than believing you possess superior firepower when you really don't know what kind of enemy you face. See rule #6. 
3. There are weapons everywhere lying around that can be improvised quickly if a person can break their freeze and react more rapidly than you can. Most people, especially nurses and doctors [who carefully study and work with anatomy everyday], instinctively, reflexively know something about how to attack pressure points or weak areas. That means every confrontation with another person could rapidly escalate into an deadly confrontation. See rule #6. 
4. Nobody else has to follow your rules or the rules of your jurisdiction. Laws are things that idiots debate. People behave according to their own rules ... there are no referees or rules in fights ... prison might be a deterrence for you, but it is not a deterrence to many people ... there are no fouls, no free throws or penalty shots, no rematches -- there doesn't have to be a next time ... it doesn't matter if the other guy cheats. See rule #6.
5. You might believe that your understanding of the rules of physics or human physiology or martial arts and fighting with weapons will govern most things, but your understanding is severely limited, biased and flawed.  See rule #6.
6. If you are still alive, there is ONLY one reason. God ALWAYS bats last.