Time passes quickly; time passes easily.
Baiju: a white young horse, metaphorically referring to the sun.
Pre-Qin Zhuangzhou's "Zhuangzi Zhibeiyou": "The gap between heaven and earth in life is like the passing of a white horse, all of a sudden."
The white horse galloped across the gap, and he galloped through the gap of her youth like the wind.
Purpose: We all must learn to accept the regrets of life and youth.