The answer to this question depends on the specific poem being referred to, which is not mentioned in the question. The search results provide different interpretations of the "sadness" referred to in different poems. For example, in the poem "Keeping Quiet," the sadness is described as the pain of not understanding oneself and not having any time for oneself. In another poem, the sadness may be related to grief, loss, heartbreak, loneliness, or other emotions. Therefore, without more information about the specific poem being referred to, it is not possible to provide a definitive answer to this question.