The mood of the author of this poem changes rapidly: the first four sentences are sadness, the last six are joy, the author's resentment is under the bell and drum, and the "main" sentence expresses the author's wild feelings from the end, that is, sadness, joy, anger and wildness, and all these emotions are based on a word "sadness". The author laments that time flies because of sadness, and also because of sadness.