There are multiple poems that refer to sadness, so the answer to this question depends on which poem is being referred to. However, based on the search results, it seems that the question is likely referring to the poem "Keeping Quiet." In this poem, the sadness that the poet refers to is the sadness of failing to understand oneself and nature, and the rush to outdo others that has made us forget the values of humanity. The poet laments that rash actions are always disastrous and harmful, and that all disasters are created by humans. The sadness in this poem is related to the pain of not having any time for oneself and not understanding oneself or ones actions.