Metaphor is the formation of a situation and a famous aphorism accumulated and brewed for a long time.
Rome was not built in a day, but the iron pestle was ground into a needle, and Gong Yu moved the riverbank thousands of miles away and was destroyed by the waves of the ant nest. The sentence in Wang Chong's Lun Heng and Xing Zuo: "The river is not cold in a day; It is indispensable to accumulate soil into mountains. "