In the Six Dynasties, the famous talker Liu Zun talked a lot, but he also admired people who didn't talk. He was very happy to see Jiang Quan not speaking often, and said: Jiang Quan can't speak, but it's really admirable to be able to not speak. Jiang Quan knew that he was not talking, but he knew how to hide. Not everyone knows where his shortcomings are, so as to be a teacher, there are countless people who can talk about it. It is excusable to be able to talk and love to talk; many people know that they are not good at talking. It happens that they keep talking and explode their shortness, which is often annoying. 
It's a kind of self-knowledge that can't speak without saying it
 it can be said that Jiang Quan's doing this is actually an extremely rare kind of intelligence.