What are some famous sayings about not studying well as a child and regretting it when you grow up?

If young people don’t work hard, old people will be sad. ——"Collection of Yuefu Poems·Long Song Xing"

Black-haired people don't know how to study diligently early, and white-haired people regret studying late. ——Yan Zhenqing's "Encouraging Learning"

Don't wait for a while, the young man's head will turn gray, and there will be no sorrow! ——Yue Fei's "Man Jiang Hong"

Young people don't know how to study hard, and when they are old they will regret studying. ——Yan Zhenqing's "Encouraging Learning"

It is easy for a young person to learn but hard for an old person to succeed, and an inch of time should not be taken lightly. ——Zhu Xi's "Occasionally"

I advise you not to cherish your gold-threaded clothes. I advise you to cherish your youth. ——Du Qiuniang's "Golden Threaded Clothes"

If I had known today, I would have regretted it. ——Shi Naian's "Water Margin"

Don't take it but don't regret it later. ——Shi Naian's "Water Margin"

When we sigh for the youth that will never return, we should consider the aging in the future and not regret for not cherishing our prime years. ——La Bruyère

There is nothing more precious and valuable than time, so don’t put off what you do today until tomorrow. ——Beethoven

My life has a limit, but my knowledge has no limit. ——Zhuangzi

There are three steps of time: the future is belated, the present flies like an arrow, and the past stands still forever. ——Schiller

Time is life, time is speed, and time is power. ——Guo Moruo

Time is given twenty-four hours a day, but one day brings wisdom and strength to the diligent, leaving only regret to the lazy. ——Lu Xun

The fastest and slowest, the longest and shortest, the most ordinary and precious, the most easily overlooked, and the most regrettable thing in the world is time. ——Golky