I think it's pretty evident the blackbird is a metaphor for depression, sitting inside his chest and causing great pain. He's trying to bear it, but eventually it starts to show through (Its wingtips push across my lungs and fill them full of feathers/Now they poke between my teeth and that's why I thirst).
Finally, when he's just given up, he asks that at least the bird be killed or driven out, regardless of how it may harm him, as the bird has just been destroying him and his life for so long at this point that he doesn't care anymore. But then he's also acknowledging that he has said some things during this depression, or maybe will later, or possibly is referring to something he wrote (a suicide note?) when talking about the bird writing. He's saying that it wasn't really him saying any of those things, it was all the bird, the depression.
I think it's pretty evident the blackbird is a metaphor for depression, sitting inside his chest and causing great pain. He's trying to bear it, but eventually it starts to show through (Its wingtips push across my lungs and fill them full of feathers/Now they poke between my teeth and that's why I thirst).
Finally, when he's just given up, he asks that at least the bird be killed or driven out, regardless of how it may harm him, as the bird has just been destroying him and his life for so long at this point that he doesn't care anymore. But then he's also acknowledging that he has said some things during this depression, or maybe will later, or possibly is referring to something he wrote (a suicide note?) when talking about the bird writing. He's saying that it wasn't really him saying any of those things, it was all the bird, the depression.