Knowledge brings Pain

King Solomon said that when you add knowledge you add pain. It's a very abstract idea that sounds debatable but in one of Rebbe Nachman of Breslov's stories he explains it so simply that I find it's the best illustration of this point:
The Sophisticate was constantly full of pain and suffering. He had a reputation for being an outstanding sage, a master craftsman and a doctor. A certain nobleman came and ordered a gold ring. The Sophisticate made a very wonderful ring engraved with extraordinary designs including an amazing tree. But when the nobleman came, he did not like the ring at all. The Sophisticate suffered terribly, because he knew that in Spain such a ring with a tree like this would be considered quite outstanding.

Another time a great nobleman arrived bringing a very expensive jewel from a far-off land. He also had another precious stone engraved with a certain design, and instructed him to engrave the same design on the jewel he had brought. The Sophisticate engraved exactly the same design on the jewel except that he made one change that nobody besides himself could possibly notice. The nobleman came and took the stone and was delighted, but the Sophisticate suffered terrible pain because of his mistake. "I have attained such a level of wisdom - how could I accidentally make a mistake?"
[source: Azamra - The Sophisticate and the Simpleton]