Two friends were walking through the desert. At one point，they had an argument， and the first friend slapped the other in the face. The other friend was hurt， but quietly he wrote in the sand:“Today my best friend slapped me in the face”

They kept walking ， until they found an oasis. There they decided to cool off and swim. The other friend started drowning， But his friend saved him. After he recovered from the near drowning， he wrote on a stone:“Today my best friend saved my life\"

The friend， who had both slapped and saved his best friend， asked him， \"After I hurt you， you wrote in the sand， and now， you write on a stone， why?\" The other friend replied:“When someone hurts us ，we should write it down in sand， where the winds of time and forgiveness can erase it. But when someone does something good for us， we must engrave it in stone，where no wind can ever erase it.\"