The speaker is warning someone who says "I love you." Instead of accepting that love, they describe themselves as glass: fragile, but also sharp, something that will cut whoever holds it too closely. It reads like a confession and a defence at once. By announcing the danger up front, the speaker tries to push the other person away before any harm is done.
The ending shows the warning wasn't enough. The other person says "I love you" again, ignoring what they've been told, and "start[s] to bleed." The wounding seems to happen almost at once, as if the speaker's prediction comes true simply because love is offered. Then comes the quiet, lowercase "and leave," which is ambiguous: it could be the lover walking away, or the speaker retreating. The short lines and the breaks between them make the poem feel hesitant and bruised. The mood is sad and tense, shaped by self-protection, guilt, and the sense that being loved can feel like a risk to both people.