A speaker writes a goodbye note to someone, then talks themselves out of ever delivering it. The lines are short and flat, almost like a person thinking out loud: they'll throw it in the bin, it's rubbish anyway, the other person won't see it. By the end, the plan is simply to leave "like normal," as if nothing has happened.
The speaker seems to feel a mix of pain, shame and quiet resignation. The aside under the title, "my hands are shaking," suggests how much this costs them, even though the words on the page are so calm. The title adds to this, with the image of flowers thrown out the window hinting at a gesture of love or hope being cast aside.
The mood is hushed and heavy. What stands out is the gap between what the speaker feels and what they let anyone see. "Goodbye" could mean leaving a relationship, and the poem's careful ambiguity leaves room for it to mean something more.