It is taught in Pure Krav Maga seminars.
Victory in Self Defense is when you control your opponent and you do whatever you can to stop him from harming you in any way possible. Your best option would be to harm him before he harm you, but you might have to evade his first move not to get hurt and be able to harm you.
Since normally in these scenarios you are alone in-charge of your fate, you need to use your own judgment about the best course of action, and how much force to use.
As a rule of thumb it might be better to use too much than too little force, as it might only be your split chance second to save yourself.
Sports Fighting is a game where you have a referee and rules that dictate your options and judgment that collectively stops your opponent form threatening your life.
Just like in a society where collective rules are devised to protect its citizens, designed to deter the folks from constantly needing to engage in self defense activity. However there are always exceptions to the norm, as we witness in our daily news.