A father had a son who would never listen or behave. One day, the father decided to hammer a nail into the door frame for each bad behavior of his son. When the frame has been filled - the man called his son and showed his bad behaviour 'proof'. The son realized how much he was made his parents suffer and promised to do a good deed every day, so the frame will be nail-free.
The moment his father took the last nail out, he started to cry.
- Father, why are you crying now? asked the young man, puzzled
- The nails are gone, my son, but the marks are still there!
This story doesn't need an explanation or a morale... just a kind reminder: before you say or do anything ask yourself "what are the marks you'll leave behind?"