“We feel sad because we cry” is a famous saying from the American philosopher William James.

He believes that we usually think that we cry because we feel sad, but in fact, we feel sad because we cry, that is, our emotional state is usually based on our external behavior. It is not constructed from inner feelings. This idea also has some support in psychology, because behavior can affect our emotional state, and emotional state can in turn affect our behavior.

There is a similar passage in the classic book "The Little Prince". In the book, the little prince meets the fox, and the fox tells the little prince: "If you tame me, then we need each other, and you will be The only person in my life, in your eyes, I am also the only fox in your life. But you need to spend time to consider me to make me unique. If you tame me, my life will be full of sunshine. Your mood will also brighten up."