It's not simple enough, however, to process cognitively when you are under attack. Take a good class on self defense law. Read your local statutes (and if you can't find them, current jury instructions). If this is your job, read your policy and procedure at least twice a year. Force law and policy is one of those things where knowing isn't good enough, you must understand.
Read to make sure it makes sense to you. Read to find anywhere that your personal ethics don't jibe with the rules. And absolutely read to see if you are training outside the rules. There is always a possibility that anyone who uses force might end up in prison. To deliberately train TO go to prison is stupid and completely avoidable. Finding these glitches and working them out lays the groundwork for something else, something important.
Most people, if they have a will to survive and an ethical base, make very good force decisions. The problem is that it is often easier to make a good decision than to explain a good decision. You will be expected, even required, to explain a subconscious, lightning-fast decision as if it was the product of extensive tactical and moral deliberation.
Most of your decisions will be good. Most of your articulations will be crap. Unless you not only learn but practice.
The scenario is a potential build-up to a 'bonding group monkey dance' (BGMD). The principal (student) is a nice guy, intelligent. I've seen his good tactical awareness and martial skills all weekend. The goal of the scenario is to push to see if he recognizes the important decision points, to see whether he runs or fight and to have him explain his decisions to the peer jury.
We come on the scene as three young, slightly drunk men, talking and laughing. Size him up. He looks interesting, might be some fun. We start talking, getting closer. The principal maintains his distance, keeps his hands in an unobstrusive 'fence' position and tries to take himself out of our social dynamic by saying a few words in what sounds like Russian.
I pounce on that, talking back in Russian, introducing M, who speaks more than I do. The principal backs up. I close and reach out. He y-strikes me in the throat, starts to run, returns, tries to run the other way, engages briefly with one of the others. I turn on him. He launches a roundhouse kick into my ribs. I take him down.
The safety calls the safety word and we stop. We are on the ground, too close to obstructions. It's a good point to end it anyway.
It is time for the principal to explain his actions tactically and legally-- especially a pre-emptive strike to the throat, something my lawyers are certain to characterize as deadly force.
Other than the running away and running back, which was almost certainly a subconscious response to 'this is training, I can't just leave' no decisions here were necessarily bad. But the decisions needed to be explained in such a way that a jury, most of whom haven't been in a fight since junior high, can understand why there was no choice. That sort of explaining is a skill.
Even led through the important points (Intent, Means, Opportunity, Preclusion; factors and circumstances that increased the danger) it was hard for the principal to put it into words.
We talked about it with the whole class: Remember, WE were the bad guys here. The three of us. He was waiting for his train, minding his own business. WE approached HIM. WE closed the distance. We had every intention of "having a little fun." But turning to the peer jury a rambling, indecisive explanation made the actions look doubtful. As Lawdog wrote; "A good report can't make a bad shoot into a good shoot, but a shitty report can turn a good shoot into a bad shoot."
The nail in the coffin, this is what I, as the bad guy, would have told a jury:
"Me and my friends were just out having a good time, you know? We were in a good mood, looking to catch the last train and we saw this dude just standing there so we thought we'd say 'hi' and the dude started talking in Russian, so I thought, "Cool, I know a little Russian and M is from that part of the world and speaks some so I said 'Hi' like, in Roosky, and the dude started acting really weird like with his hands up and acting all agitated so I put my hands up to try to calm him down and WHAM out of nowhere he chops me in the throat and I started gagging and couldn't breath. Then he runs and I know he told you he was running away but it looked like he was running right at M and M is a little guy and doesn't see to well so I grabbed the dude from behind to pull him off and he kicked me some kind of karate kick so I think he was a really dangerous martial artist and the kick hurt so I just grabbed on to the leg and we fell down..."
I have extensive practice explaining this stuff, both in the dry, boring report form of a Use of Force Report: "The subject (6'2" 234 pounds) raised his clench fist and said "I'm going to kill you, motherfucker" I noticed that his lips were drawn back showing his teeth and he was sweating. I stepped in quickly with my left foot and raised my right hand catching the arm he was threatening me with under the armpit and turning his body..."
And also in the emotional vein I have heard from so many bad guys justifying their actions. By the time the peer jury heard my story (the observable things in the story were true) they were on my side. Damn.
Doing things right is the first step. You also need to explain them. He should have won the articulation war. He was in the right. He was the good guy. It was just a part that I had trained and he (and almost all martial artists) had not.
I'm not going to go into all the details of articulation here. Don't have the time or the space. But be aware that the hole exists and start thinking about it now.