The song is about a memory, but it's mostly about killing a memory. He's denying that this girl ever meant anything to him. She's not even given a name, she's "black coffee in bed". He's claiming that all she left behind is a coffee stain. We know it's a lie but it's a lie he's trying to sell himself. He even claims to be on to the next girl but we know he's not. He's constantly remembering something, a perspective-changing experience of intimacy, he's constantly trying to forget.
The song is about a memory, but it's mostly about killing a memory. He's denying that this girl ever meant anything to him. She's not even given a name, she's "black coffee in bed". He's claiming that all she left behind is a coffee stain. We know it's a lie but it's a lie he's trying to sell himself. He even claims to be on to the next girl but we know he's not. He's constantly remembering something, a perspective-changing experience of intimacy, he's constantly trying to forget.