One day, Little Johnny walked …

One day, Little Johnny walked up to his mother and and began to look at her hair. He studied it for a moment then sadly said: “Mom, why is it that some of your hair is white?”
His mother replied, “Well, every time that you do something wrong and make me cry or unhappy, one of my hairs turns white.
Little Johnny thought about this revelation a while, and then said, “I guess I can imagine how come ALL of grandma’s hairs are white!”