For me, it's about a relationship that breaks up (or down?) because of the narrator's drug abuse.
"Down so long", "working on a plan" are typical of the intentions of those trying to recover from addiction, along with the idea of "catching up" to the person they're estranged from ("some day I'm gonna get where you are"). If in any doubt that it's about addiction, the line "brain so cooked") should confirm it.
For me, it's about a relationship that breaks up (or down?) because of the narrator's drug abuse.
"Down so long", "working on a plan" are typical of the intentions of those trying to recover from addiction, along with the idea of "catching up" to the person they're estranged from ("some day I'm gonna get where you are"). If in any doubt that it's about addiction, the line "brain so cooked") should confirm it.