This story is being told in many cultures and attributed to many famous people (including the wise King Solomon).
Long time ago there was a wise King. He was a good ruler and taking good care of his people. However, one day it came to his attention that a soldier in his army was wiser than the King. Jealousy washed over the King and he thought of a way to show the soldier wasn't wiser than himself.
One day, the King called the soldier and explained he heard there is a ring that holds the wisdom of the whole world: if the wearer is sad, the ring will make him happy, if the wearer is happy, the ring will make him sad. The soldier was sent to find the ring, while the King was sure the task is impossible and the soldier will return empty-handed and everyone will recognize the King to be the wisest person on earth.
After searching everywhere, the soldier could not find such a ring. He decided to return back home and face his fate, without the precious ring. On his way back - he stopped in a village and the silversmith asked him why the sadness. The soldier explained the whole story and the silversmith laughed and went back into his place. After a little while - he returned with a ring.
The soldier - took a look at the ring and started laughing. He thanked the villager and returned quickly to the palace.
The King was quite happy and smug - sure the task is impossible. When he received the ring, after a quick glance, he became quite sad.
What was about the special ring? It had an inscription: "This too shall pass".
A bitter-sweet message: make sure you enjoy your every moment of happiness. If you're unhappy: remember: this too shall pass!