In the poem's final stanza, the speaker explains that there are many things he does not understand about his love for the listener, such as where it comes from or how it exists. Moreover, his love isn't burdened by worries or by his own pride. He doesn't believe there's any real alternative to this all-consuming, intense version of love, which is so powerful that it obliterates distinctions between him and his lover. As a result, their bodies feel interchangeable—his lover's hand draped over him feels like his own. Their minds also feel interchangeable—when his lover closes her eyes to sleep, she witnesses the speaker's dreams.
The start of the third stanza makes it seem as if it will be a fairly smooth continuation of the patterns set by the first two. Those first two stanzas begin, respectively, with the similar phrases "I don't love you" and "I love you," whereas this stanza begins with the words "I love you." In other words, it doesn't look like it will be much of a departure from the previous eight lines. But this is a sonnet, after all, and that lets us know that a change, or a volta, is coming. Just as we're transitioning from clipped quatrains into a longer sestet, we're transitioning in terms of the speaker's goals. He's no longer seeking the perfect metaphorical representation of his feelings. Instead, he's embraced literal language, as if realizing that his love is too great and too forceful to leave any room for poetic flourishes. His statements here are bald and unflinching, with almost no imagery at all: "I love you like this because I don’t know any other way to love," for instance.
The immediacy of this language, in which images are rejected and no longer serve as intermediaries with which to convey abstract experience, reflects the immediacy of the speaker's love. There are, he explains, no longer any intermediaries between himself and his lover. Their bodies, rather than serving as instruments of connection and communication, actually become a single entity. And while a more traditional or more cliche poem might describe lovers dreaming about one another, this pair goes a step further, sharing the same dreams.
The switch from quatrains to a sestet alerts us to an accompanying change in focus, but the longer stanza also creates a tonal shift. The neat four-line stanzas that open the poem feel more controlled than the six-line stanza that follows. As the speaker accepts the impossibility of finding suitable figurative language, he also seems to let loose, abandoning the formal constraints that characterized the first two stanzas. This shift is subtle rather than dramatic. End-stopped lines keep the last stanza from feeling disorderly, so that the speaker appears to be calm and in control, and more relaxed and willing to follow his emotions where they lead.