Here, the speaker admits to failing someone they loved. By comparing themselves to Achilles, who in Homer's story lost his friend Patroclus, they cast their own pride and carelessness as the cause of a loss. But the poem soon revises that claim. In the final lines, the speaker says it wasn't pride that ended things, but blindness: they simply didn't notice the other person's pain, thoughts, or tears.
The speaker feels guilt and regret, and a quiet humility. They don't ask for forgiveness. Instead, they wish the other person a happier life with people who will notice and care for them in ways the speaker couldn't. The mood is sorrowful and bare. The short, plain lines feel like a confession spoken without defense. The shift from "killed us" to "killed you" at the end is the sharpest moment, as if the speaker finally sees how much damage was done.