Some children were playing on the beach. They made castles of sand, and each child defended his castle and said, "This one is mine!"
They kept their castles separate and would not allow any mistakes about which was whose. When the castles were all finished, one child kicked over someone else's castle and completely destroyed it. The owner of the castle flew into a rage, pulled the other child's hair, struck him with his fist and bawled out, "He has spoiled my castle! Come along all of you and help me to punish him as he deserves." The others all came to his help. They beat the guilty child mercilessly.
Then, they all went on playing in their sand castles, each saying, "This is mine! No one else may have it. Keep away! Don't touch my castle!"
But the evening came and it was getting dark. The children thought they ought to be going home. No one now cared what became of his castle. One child stamped on his, another pushed his over with both hands. Then they turned away and went back, each to his home thinking that what they did not destroy will be destroyed by the waves.
In this parable, Enlightenment is likened to the overcoming of the passion for existence with the cool evening. In the Pali version, the sand castles are likened to the body, which had been the object of grasping. After Awakening the body becomes a thing to be discarded and broken up, and eventually abandoned when life ends.
Yogacara Bhumi Sutra 4 (Quoted from World Scripture)