Myth 1. You can empty your clip into the knife guy before he can move two steps.
Reality: People don't test well under pressure. They tend to miss more and sometimes freeze, screw up or run for their lives screaming like little boys.
Myth 2. The knife guy will drop like a sack of potatoes when you shoot him.
Reality: Sometimes they drop, sometimes they take multiple hits and act like nothing happened.
Myth 3. Your awareness is so keen no one will ever get that close to you.
Reality: They can get close to you before you have a clue. Distractions can take many forms. There are a lot of variables out there in this big world. Don't count on your awareness. Some people can't even count on having a gun on them.
Myth 4. The knife guy running at you will just run straight whatever you do.
Reality: If you move, don't forget he can move too.
Myth 5. A gun beats a knife.
Reality: It all depends on where the bullet hits and where the knife or machete hits. If he has a bullet hole in the stomach and your head is detached from your body, did you win? If he is dead and your eyes have been slashed by a knife, did you "win"? Many officers have been severely injured by knives. Don't think your gun is a magic wand.