They often tell you that experience is the best teacher, but they never tell you why.
I'm a professional swindler--oops, public high school social studies teacher--and I know something about how people learn. If a kid comes into my class interested in learning something about the subject matter, willing to listen, and willing to open the book, I or any other fool can teach him.
But then there's Mr. Experience--his job is to teach those who neither listen to their elders nor read. Their number is legion, and they can't learn from anyone else.