The speaker replays a single moment: holding someone who felt unwell, their head against his chest, makeup rubbing off on his shirt. He doesn't mind the stain. He feels peaceful, even as he wants the other person to get better and, at the same time, not to leave. Small details carry the weight here: the curve of a lower back, the brush of hair on his arm, a smell he can't forget. It's all new to him, and he says so plainly.
Then the poem shifts. The moment ended for her, but "it never ends for me." He admits he could have kept her close if he had tried, and the rest of the poem becomes a string of "I imagine" lines. They kiss, they don't, she stays, she loves him. The last line, "i imagine you're here i imagine you aren't," leaves him between wish and reality. The mood is tender and wistful, tinged with regret. The lack of punctuation makes it feel like a thought spilling out without pause.