Broken agreement

A boy and a girl were playing together. The boy had a collection of marbles and the girl had some sweets. The boy told the girl that he would give her all his marbles in exchange for all her sweets, and the girl agreed. 

However, the boy kept the most beautiful and the biggest marbles with him and gave her the remaining marbles. The girl gave him all her sweets as she promised. 

That night, the girl slept peacefully. The boy could not sleep, as he kept wondering if the girl had hidden some sweets from him, the way he had hidden the best marbles from her.

Author Unknown

Source: The School of Practical Philosophy