The Sky (Symbol)
The sky symbolizes the indifference of the natural world in the face of human feelings and circumstances. When the speaker is happy and in love, the sky's endlessness feels thrilling, like a reflection of his love itself. But when he is lonely and abandoned, the sky feels remote, forbidding, and cold. The sky itself, of course, hasn't changed. In fact, the speaker goes out of his way to note that it looks exactly the same in both of these situations. Thus, no matter what the speaker projects onto nature, nature itself is unaltered and unresponsive. The speaker's changing reactions are purely personal, requiring no input from the natural world. For better or for worse, then, nature appears to be completely insensitive to human needs.
Language (Motif)
The speaker is extremely upset because his lover has left him, and claims that, because of his mood, he is able to write "the saddest lines." In other words, he seems to believe that he will have no trouble putting his feelings into language. But that's evidently untrue. His speech is burdened by pauses, expressed in short lines and terse sentences, as if using language at all is extremely difficult. The extreme emotions that make him feel the need to express himself actually make self-expression harder. In fact, he says, "verse falls to the soul like dew to the pasture," as if he lacks control over the formation of the verse itself. This produces a fascinating paradox. The less eloquent the speaker's linguistic expressions of sadness, the sadder he appears, because his inability to express himself through language is in itself rooted in intense sadness. Thus, his failure to write the "saddest lines" produces extremely, if understatedly, sad lines.
