Unpredictability and vulnerability

Remember that the professional may be predictable, but the world is full of amateurs.

So, while you work with and against "trained" fighters, your attacker will almost certainly be of the "untrained" variety. Does that make them less dangerous? Don't bet your life on it!

The street thug has learned his craft well, by actually employing his strategy against real victims in real circumstances. He knows what works and when it works, which gives him a huge dose of confidence.

Unorthodox or unexpected attacks can cause havoc with your "trained" responses.

I once saw Royce Gracie almost get KO'ed in a seminar (this was during the height of his UFC fighting days) when a raw beginner did a completely unexpected move and kneed Royce right in the face. The kid was not being malicious, it's just that he had no idea of what to do next so he did something completely unpredictable.

Expect the unexpected.