There is a story of two friends who were walking through a desert.
At a certain point of the journey they had an argument, and one friend slapped the other one right across the face. The one who got slapped was very hurt, but without saying anything, wrote in the sand:
“Today my closest friend slapped me.”
The two friends kept on walking until they found an oasis, where they decided to go into the water.
The one, who had been slapped, got stuck in the mire and started drowning, but his friend saved him. After the friend recovered from near drowning, he carved out on a stone:
“Today my closest friend saved my life.”
The friend who had 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 winds of forgiveness can erase it away.
“But, when someone does something good for us, we must engrave it in stone where no wind can ever erase it.”