If you were born like an ant, you should know that your life is thinner than paper and you should not be taller than the sky. What do you mean, you and I are both cows and horses?

This sentence is a metaphor, which roughly means that although life is as insignificant as ants, we should have self-knowledge and realize that our fate is thinner than paper, and we should not have too high ambitions and expectations. Because Gankun (referring to heaven and earth) is doomed, we are all ordinary people like cattle and horses. This sentence expresses the helplessness to reality and resigned attitude.