The little devil tells jokes.

My understanding is: where others look down on you, you also look down on yourself, but you should turn this into your strength. Take the little devil himself, for example. A dwarf is the place where others look down on him. When others laughed at him as a dwarf, he was relieved, because it was an unchangeable fact. Since we can't change it, we must make rational use of it. The little devil can't become a knight like his brother Zhan Mu, but he can learn by reading, so he "armed himself". Facts have also proved that he is one of the smartest people in the Lannister family and even in the book.