2. Work hard, then decline, and finally run out. It means: on the first drum, courage will cheer up, on the second drum, courage will drop, and on the third drum, courage will be gone. Metaphor at the last moment, get things done at once.
There is no such thing as America. Meaning: in melon, the melon land is also bitter, which shows that everything in the world is not perfect.
4. Those who plant trees must cultivate their roots, and those who plant virtues must cultivate their hearts. It means: to plant a tree, you must cultivate its roots, and to teach people must cultivate its thoughts. Explain that watering trees requires watering roots, and educating people requires nourishing the heart.
5. Know the sound after holding a thousand songs, and know the instrument after watching a thousand swords. It means: You don't know the beauty of music until you practice a thousand pieces of music, and you can tell the quality of weapons only by looking at a thousand swords. This shows that more practice can produce true knowledge.