What is the poem in the long song line that warns people not to idle away their time?

In the long song line, the poem that warns people not to idle away their time is "Young people don't work hard, but old people are sad."

A lazy youth, a lousy age. They all say that they don't work hard when they are young and strong. It's no use being sad when you are old. Source "Yuefu Poems and Long Songs": "When will a hundred rivers go east to the sea and return to the West? If you don't work hard, the boss will be sad. " Han Yuefu wrote about dynasties and the Han Dynasty.

Interpretation: It is useless to study if you don't work hard when you are young and strong.

Remind us to cherish time and not to waste it. It is also used to warn us to work hard while we are young, and not to achieve nothing when we are old, leaving only sadness and regret.