The speaker opens by insisting they were over someone, then spends the rest of the poem showing they aren't. Memories keep coming back, and the constant nausea suggests guilt as much as heartbreak. The speaker admits to a mistake ("I fucked up") and seems to regret something they said, since their last words to this person were "Not like it matters anyway." Right after, they correct themselves: "But it mattered." That reversal is the emotional center of the poem.
The lines break off in places, like "What did you mean when you said," which makes the poem feel like a mind circling a painful moment and never getting a clear answer. Then a flicker of hope arrives: the heart "leaped," almost jumping out of a "gaping mouth," a physical image of shock and longing. Repeating the opening line at the end turns it from a confident claim into something closer to a confession. The mood is raw, anxious, and regretful, with hope that hurts as much as it comforts.