A man was out walking in the desert when a voice said to him, "Pick up some pebbles and put them in your pocket, and tomorrow you will be both happy and sad."
The man obeyed. He stooped down and picked up a handful of pebbles and put them in his pocket.
The next morning he reached into his pocket and found diamonds and rubies and emeralds. And he was both happy and sad. Happy he had taken some - sad that he hadn't taken more. And so it is with knowledge.
- Source Unknown