The real secrets to fighting exist in understanding principles and remain hidden to us in plain sight. Most teachers just don't know about them they think all lies in technique and endless conditioning. Instead the secret lies in understanding.
The problem I see with that is too many people too focused on being strong, fast and aggressive (nothing wrong with all of these) which is like training with no direction toward understanding. When somebody comes along who is stronger faster and more aggressive; we're dead.
Principles have no form and that makes things tricky.
Now fighting and martial arts is one of the stupidest acitvities we can do as human beings, aside from killing one another. Fighting is brutal and ugly and for some reason our training methods seem to follow suit and not allow for much intelligence, beauty and skill.
The main reason I see people not learning skill is they are too busy trying to win, look good, and they believe what they are taught without questioning or experimentation, or they are just too dumb to realize there is something else out there. A world of fighting possibility that would blow them away if they gave it a chance.
There are some who are starting to learn fighting with intelligence in mind. It shows up in the fighters with skill. In my opinion a few of these are, Bruce Lee (unfortunately hes dead), Muhammad Ali (clearly skillful), Eddie Bravo (Understands principles like, Staying Tight, Following; "when they move you move with them," "Anaconda mode..." etc..) Denney Prokopos, Anderson Sylva (he knocked out Forrest Griffin while backing up), BJ Penn (His skill and manuverability on the ground and standing up are incredible), to name a few. I have also seen Quinten Jackson start to move his head instead of block.
The secret to mastering fighting lies in powerfully understanding principles that govern and create interaction. It requires a shift in mind that creates a reality in which you win and your opponent loses. Check this out.