Poetry with educational and warning significance

1. When will the Hundred Rivers enter the sea in the east and return to the west? A lazy youth, a lousy age. -Han Yuefu's "Long Songs")

2, the light is midnight chicken, it is the time for men to study. Teenagers only know how to play, but don't know how to study hard. When they are old, they regret why they didn't know how to study hard when they were young. Yan Zhenqing's Persuasion

3, the ancients learned nothing, suitable for all ages. What you get on paper is so shallow that you never know what you have to do. Lu You reads books in winter nights and shows them to children.