Black-haired people don’t know how to study early, and white-haired people regret studying late.
When you are young, you must know how to study hard and study diligently. But if you only know how to play and don't know how to study hard, you will regret when you are old that you didn't know how to study hard when you were young.
"Encouragement to Study" is an ancient poem written by Yan Zhenqing, a poet of the Tang Dynasty. Black-haired people don't know how to study diligently early, and white-haired people regret studying late.