That is to say, people are not as ferocious as jackals, as powerful as tigers, and even the wild ghosts in the dry spring are afraid. However, people are not afraid of tigers, wolves' faces, and they are afraid of knowing people's faces but not their hearts. When you meet a duplicitous friend, you are not afraid of meeting the real bad guy, but afraid of meeting the fake good guy. Can also be understood as, make friends, don't make friends with two-faced people, you are sincere to him, he won't be sincere to you, he inadvertently paid his sincerity by mistake and mistook the bad guys for the good guys. The human heart is sometimes more cruel than wolves and tigers, and even more bizarre than ghosts.