When I was very young I remember telling a lie about to a friend about someone we had had a falling out with, I didnt realise he had spoken and made up wih this friend and it caused him to fall out with him again. I was full of guilt and didnt have the balls to own up.
As penance I vowed never to lie which got me into plenty of trouble later on as well as a few groudings, on the other hand I gained a reputation among my peers for being trustworthy and honest. It did teach me that words have power and what you say can hurt others so I was always careful about what I said. Its a lesson thats stuck with me.