Darren said in an interview that he was once in an abusive relationship and some time after it ended, the other person sent him this long and hurtful email telling him all the reasons why it never worked. He wrote out this long and heartfelt response but never sent it, and this song is nearly word-for-word what that reply would have said.
This song touches me very much because I've had people make me feel the way he describes having felt. It's devastating.