What do you mean, Castle Peak, Fast Horse and Happy Fairy?

The galloping horse on the green hill is a poem, which means that the horse on the green hill runs very fast, and the carp in the running water swims for a long time, and finally becomes far away and can't catch up. However, carefree immortals can fly thousands of miles freely and will soon disappear. This poem expresses a strong, short-lived and erratic mood and state, which is often used to describe the rapid development and sudden disappearance of certain things or individuals.