Intestinal Fortitude?

I used this phrase in something I just wrote and began to think about what this really means.

In mammals (including humans) there is a mechanism for survival when threatened. And this mechanism is explosively defecating and urinating to drop weight suddenly to be lighter and faster when you suddenly run from danger. This is a very important survival mechanism when we were being chased by a Rhino or Saber Toothed Tiger. It might have meant the difference between survival and death.

However, when humans organized for battle this became more of a nuisance and a problem. Because what was once useful was not useful at least among men getting ready for battle. So, the term intestinal fortitude came to mean someone who could keep their bowels and bladder from exploding even when they were really really scared. However, in the end one can either fight, fight and then run or just run depending upon how bad the situation is at any point at all in life.

And sometimes we are right to fight and sometimes we are not. And sometimes we live and sometimes we die whether or not we fight or we run.