sand and stone

The story goes that two friends are walking through the desert. During some point of the journey they have an argument, and one friend slap the other one in the face.The one is hurt, but without saying anything, he writes in the sand: "Today my best friend slaps me in the face."
They keep on walking until they find an oasis and they decide to take a bath. The one who has been slapped gets stuck in the mire and starts drowning, but the friend saves him.After he recovers from the near drowning, he writes on a stone: "Today my best friend saves my life."His friend askes him, "After I hurt you, you write in the sand and now you write on a stone. Why?"
He replies: "When someone hurts us we should write it down in the sand, the winds of forgiveness can erase it away. But when someone does something good for us, we must engrave it in a stone，therefore，no wind can ever erase it."Learn to write your hurts in the sand an!d to carve your benefits on the stone.