Long song is a folk song of () generation. What does the poem mean by "water flows into the sea and never returns"? Explain? Persuade people to want it.

Long Songs is a folk song of Yuefu in Han Dynasty. The last poem is that if young people don't work hard, old people will be sad. Express the poet's feelings about the passage of time and inspire the world to cherish time and make a difference. Convince us.

Young people should cherish time. If they don't work hard when they are young, it is useless to regret and grieve when they are old.