In a real life altercation, where things can be total chaos, and people are trying to make critical decisions under extreme pressure, the person with a clear mind will have an advantage.
When you are unsure, that moment of hesitation creates an opening for your opponent to take advantage of.
When I was in junior high school, one summer I went to a dormitory. There I got into my first real fight. The guy was a bully and had a very dark and twisted attitude about him. I punched him in the ribs with everything I had, then I grabbed his hair and proceeded to kick him repeatedly in the ribs with everything I had. I shoved him, I was still standing and he was balled up on the ground, and I didn't know what to do, but I knew I had to do something. First thing that came to mind was soccer kick him in the face, but it seemed too extreme, second thing was to jump up in the air and double stomp him like Bruce Lee did in Enter the Dragon, which also seemed like too much. Third was to drop an elbow to the spine, but once again it seemed like too much, plus none of these moves I was familiar with, so I hesitated, instead I punched him in his back and felt like an idiot.
I said to myself: "what in the world was that? The stupidest punch ever!" Well, he yelled out: "You win! Stop! I give up!" So I stopped and he got up extended his hand, as I reluctantly went to shake it, he punched me with the other hand, he rocked my head way back, to this day my vision do not match.
Moral of the tale, do not hesitate. In order not to hesitate, you need to know exactly what to do, you need to know what to expect, so that you can act upon a clear mind and complete your mission.
That fight took place around 1992, before the UFC. If I had known MMA, I would have been able to control him by going to the ground and wearing him down systematically. I didn't have to get the Mount and destroy his face like Pat Smith did to Scott Morris in UFC 2. However I could have had much better control. If I didn't want to commit that much at least I would have known that there was no control and I needed to leave completely or finish the job like Wanderlei Silva had done many times in PRIDE and stomped this guy, but at least I would have known, what that would be like, how far to take it, and that I wasn't going to kill the guy.
There were many things that I could have done, but either way, the main thing was I hesitated, my mind was not where it needed to be. So I was totally vulnerable.