1. Long Songs is a classical poem of China, belonging to Han Yuefu, which is a famous piece to exhort the world to cherish the time and forge ahead.
2. Seen from the overall conception, this poem mainly means that the seasons change quickly and the time is gone forever, so people are advised to cherish their youth and work hard to make a difference. The whole poem expresses feelings with scenery, and makes sense from feelings. It entrusts the philosophy of life of "Young people don't work hard, but the oldest disciples are sad" in such vivid images as morning dew is easy to dry, Qiu Lai leaves fall, and a hundred rivers go east. With the help of morning dew, flowers fall in Ye Qiu, and running water goes east and doesn't return, there is a sigh that time is fleeting and life is short, encouraging people to firmly grasp the life that flies with time and make efforts to make progress while young people are young. Its emotional tone is positive.
3. The main idea is embodied in the last two sentences, but the poet's thought is not simply expressed, but a concrete image rich in aesthetic feeling is extracted from the real world and taught in aesthetics.