What does Kuafu mean by chasing the sun?

In ancient mythology, in order to chase the sun, Kuafu was so thirsty that he drank the water from the Yellow River and Weihe River, but he went elsewhere to find water and died of thirst. The wooden staff he left behind later turned into a forest called Deng Lin (see Shan Hai Jing Overseas North Jing). Later, "Kuafu chasing the sun" was used as a metaphor for making up one's mind or overreaching.