What is the function of the metaphor at the beginning of Taiping Shengshi?

The function of the metaphor used at the beginning of "Be prepared for danger in times of peace" is to abstract the narrative into concrete, make things clearer, make sense simple and easy to understand, and make people easy to accept.

At the beginning, the article compares "governing the country" to "governing people", and then says that even if the disease is cured, it should be nursed back to health, which means that even if the state power has been established, it should be prepared for danger in times of peace, be thrifty and not extravagant, so that the river can go downhill and the Han Dynasty can maintain long-term stability.

"Be prepared for danger in times of peace" (Song Dynasty) Sima Guang, the main idea of the article is to always consider the arrival of danger in a comfortable environment.

Original text:

The courtier said, "Governing the country is like curing a disease. Although the disease has been cured, it is particularly suitable for care. If Qi indulges himself and gets sick again, it's hopeless. Today, China is endowed with unique advantages, and all the four barbarians submit, which is what we have hoped for since ancient times. However, I am cautious every day, but I am afraid, so I want to count on Wen Qing's generation to fight. "

Wei Zhi said: "I don't like internal and external security, but I like your majesty to be prepared for danger in times of peace."

Translation:

Emperor Taizong said to the ministers around him: "Governing the country is like treating a disease. Even if the disease is cured, it should be nursed back to health. If you let go of indulgence immediately, once the old disease recurs, there is no way to save it. Now this country is fortunate to have peace and tranquility, and ethnic minorities in all directions obey it. This is really rare since ancient times, but I am more and more careful every day. I am afraid that this situation will not last long, so I hope to hear your comments many times. "

Wei Zhi replied: "I don't think it is worth celebrating that both at home and abroad have been governed peacefully, but I am glad that your majesty is prepared for danger in times of peace."