Legend has it that swans sing just before they die. Someone happened to come across a swan for sale in the market. He also heard that the song of this swan was very sweet, so he bought it and took it home. One day, he held a banquet and asked the swan to sing during the dinner, but the swan never made a sound. Later, when the swan grew old and knew that his death was imminent, he sang an elegy to himself. After hearing this, the master said: "If you really refuse to sing except when you are dying, then I am too stupid. When I asked you to sing that day, I should have killed you."

Through the story of the swan and its master, we know:

Many people are unwilling to do certain things voluntarily and always do it reluctantly when they have no choice.