Law Enforcement officers opinions please?

So I am a law abiding citizen that occasionally carries a gun legally with a firearms license. I am the son of a retired Captain of Fort Lauderdale PD and have asked him the same question and now I want your advise. When adrenaline starts flowing when your going from 0-60 in a HIGHLY STRESSFUL situation, lets say in a fight OR gunfight where you know you may be hurt, you instantly have to make a decision weather to pull the trigger or not. There is NO training on the planet that makes you able to adapt to that kind of situation, weather it be qualifying on the range or at the Police Academy training. Unless you take an adrenaline shot during training which I'm sure 99 % of you haven't. I know the department and the state attorney will most likely be on your side when it comes to an officers shooting but my question is the decision you make prior to all this. Adrenaline takes over all senses the bodies decision (brain) gives off. Whats your opinion on this..All answers will be seriously taken into account. Thank you.