[cloud8a]

I have heard a thousand scenarios of the general "BG with a gun, What do you do?"
There are thousands of answers that involve a physical reaction.
The one question that racks me the most when I read through these scenarios and ask myself, "what would I do?" is how do I train myself to keep a level head?
I do not want to over react or under react in a situation that could result in death.
My friends and I used to get into fights in high school. I mastered being able to stay very clam when a fight would break out. But that was usually when the fight did not involve me. When a fight did involve me I had zero control.
I know that if I cannot naturally level off I am capable of making a mistake, and that mistake could be permanent death for the wrong person.
I am not familiar in this training area but I want to be so that I can trust myself to obtain some type of level tactical thinking in a life or death situation.
The only thing I can think of are some type of high stress live fire training on a consistent basis.
What do you guys know that could help me achieve this?