Today, my friend save me

There were two friends who were walking across a desert. While they were walking they got into an ugly argument and out of anger one of them slapped, through was hurt he did not say anything and quietly wrote over the sand "I am hurt because today my friend hit me on my face". They resumed walking and kept walking until they came across on oasis then. While they were taking bath the one who had got slapped started drowing. The other friend came to his rescue and saved him. After he got rescued, he wrote on the stone "Today I was saved by my best friend".

The other friend asked him, "Why did you write on the sand when I slapped you while you wrote on the stone when I saved you?" Upon these, the other friend replied that it's better we write on sand when your friend hurts you as it will be gone with the wind but write it on stone when your friend does something good to you so that it could be engraved forever.