I think it's about missing an ex. Maybe they started out as friends and tried to be more but when it didn't work they lost the friendship. It sounds like maybe he blames her a little and is somewhat bitter ("this song is my weapon of choice"). He tells her to remember the good times and maybe he hopes they haunt her ("My name will stay on the tip of your tongue, I will be your favorite mistake").
I think it's about missing an ex. Maybe they started out as friends and tried to be more but when it didn't work they lost the friendship. It sounds like maybe he blames her a little and is somewhat bitter ("this song is my weapon of choice"). He tells her to remember the good times and maybe he hopes they haunt her ("My name will stay on the tip of your tongue, I will be your favorite mistake").