Experience
"Experience keeps a dear school, but fools will learn in no other." Benjamin Franklin (Fools refuse to learn in school from textbooks or teachers. Fools choose to learn only from their own mistakes. They will not learn in a school classroom.) or (Experience is a great teacher and teaches many of life's most important lessons, but only fools will refuse to get new knowledge in other ways too. Examples of other ways to learn things are listening, reading, remembering, and reasoning.)