I recently got into handguns and training.
I recommend everyone who has access to it go into training where you take a real handgun that's been modified to shoot laser and has CO2 recoil. The setup is that you have a screen (perhaps all around you), playing out a scenario. You're in a convenience store, and something may happen that requires you to defend yourself.
Even with a fair amount of training, the adrenalin surge is significant, and the time you have to respond is very limited. Doing this eliminated any illusions I had regarding guns and safety. There's little time to rack the gun to put a round in the chamber. And if you haven't done it, it's not easy to rack a gun (you need the right grip, angle, etc). And racking can fail. Even I, with very limited experience, have experienced multiple failures while racking.
People mentioned videos where people practice doing all this, and time themselves. I saw a video where someone 3 yards away draws a machete and runs at the other person. The time he has to draw and defend is just not enough at 3 yards. One needs to actively dodge the machete while drawing. Adding the complexity of racking is almost a guaranteed failure. The person drawing was very experienced (and a handgun trainer), knew the attack was going to come, and still had a low success rate.
Other things I've had to unlearn:
"Why didn't they just shoot at the legs?" At short notice, in an emergency scenario, aim is very poor. People train for these situations to get a reasonable likelihood of hitting a person without needing to spend time aiming. And the primary way to do it is to aim at the body - not arms/head/legs.
"Why did they have to shoot the person 3 times?" See above. Aim is hard, and there's a good chance of missing. When your life is on the line, you are not going to shoot once and check if it hit. You'll shoot 3 rounds quickly. When I did the simulator, I often shot 4-6 rounds without even realizing it (and was told by the instructor to keep it down).
This may be hard for some to believe/digest. As I said, I didn't believe it until I was put in those (simulated) situations.
Another thing I thought was crazy: People sleeping with a loaded gun by their bed. A guy did a video where an intruder was in the house and running towards their room. They timed different scenarios (unloaded with magazine on the side, different gun safes, etc). He succeeded only with one particular gun safe, and only with the gun fully loaded.
If I ever keep a gun at home, it will not be for "defend against an intruder in the middle of the night". It's just too risky to keep a loaded gun next to your bed. But if you have good reason to believe someone is after you, this is the only way to go.
Having said all that, if I carried a gun, I'd likely not have a round in the chamber. But that's really me saying I'm not going to carry a gun for safety purposes.