The speaker has found someone who seems to be exactly right, but there's a catch: they can't be together. He is close by, "actually here," yet out of reach. The poem opens with a blunt image, a "pill" that is hard to swallow, and it's a nicely odd twist that the bitter part isn't bad news but the cruel mix of good luck and bad timing. Things have "happened the way they're supposed to," and still the speaker can't touch him.
What gives the poem its force is the last stretch. The speaker admits to wanting and needing him so much that their "bones are shaking." That physical detail makes the longing feel real, not just romantic. Behind it is a long numbness, "so many months" of believing they would never feel anything again. So the mood is a tangle: aching and frustrated, but also startled and a little grateful. The pain of wanting is, oddly, proof that the speaker is alive again.