First, some facts that go against everything about the ass-kicking fantasy we hold in our public conscious:
-Most fights are completely avoidable. They don't need to happen.
-Most fights that do happen are NOT acts of self-defense.
-Effective self-defense is more about communication, situational awareness, posturing, fleeing, and prevention, and otherwise de-escalating a conflict than actual fighting.
-If you end up in a fight (that no one is paying you for), you've already lost the most important battle.
-The best martial art for physical self-defense is track and field. Running away is 100% easier, safer, and more effective than fighting.
-Anyone willing to attack you WILL have a significant advantage. They will ether be bigger, stronger, carrying weapons, they'll bring friends, or all of the above.
-Most of the fighting techniques taught as "self-defense" only serve to further escalate a conflict.
EXAMPLE 1: If you hit your attacker and fail to knock him out cold, or otherwise subdue him completely, he will hit you back harder... and repeatedly.)
EXAMPLE 2: If you hit your attacker in the groin, this is not a grantee of victory. Yes, it's painful. And because it's painful (and personal) it will make your attacker want to hurt you even more.
-If you plan on ending a conflict with violence, get a weapon, know how to use it, and be prepared to live with the moral and legal consequences of severely injuring or killing another human being.
-Attacking someone because you're angry, someone hurt your feelings, injured your pride, or because someone "looks like they might do something" is not self-defense, it's assault and battery.
-Regardless of how skilled your attackers are: fighting one person is hard; Fighting multiple people is exponentially harder; Fighting multiple people with weapons is suicide.
-If someone threatens you with a gun or a knife asking for your money, slowly give him your money and walk away. (I've used this amazing technique 6 times in real life when accosted by gun wielding muggers and I never once got shot! You can't argue with a 100% success rate.)
-If you get into a knife fight unarmed, you WILL get stabbed... repeatedly (not "might" get stabbed, "WILL")
-If you plan on ever using fighting techniques in real life, you need to practice them consistently against live, resisting opponents. You don't have time to think in a fight, your body predominantly reacts the way you've trained your muscle memory. If you haven't actually drilled the techniques you want to use into your muscle memory, you won't be able to use them when you need them.
-If a self-defense instructor wears camouflage pants but is not actually an acting member of a military branch that requires him to wear such a uniform, there is a high possibility you are being peddled a steaming pile of crap. (I have yet to see a camo-clad civilian self-defense instructor who isn't a craptacular monger of nonsense movement.)