Once, a man went to a library. There he read a book, 'How to ride a horse'. After few days, he went to a friend who had a horse. After seeing the horse, he couldn't control himself and asked for a ride from his friend. The friend agreed.
The man tried to ride the horse. But a horse always recognizes its rider. It reared up and flung the man to the ground, every time he tried to climb up.
The friend finally asked, "Where did you learn to ride?"
The man exposed his foolishness saying, "I learned it from a library book."
Moral: We cannot learn everything on our own, and sometimes we need the guidance of a teacher.