I think this song is definitely about a person going through a deep depression, but I also think it is optimistic in that it hints that he is climbing out of his depression.
"All the fever in my brain, I'm alright now, I can even take the pain."
Meaning that despite everything, he isn't going to give up because he's learning to take the pain. Even though life is hard and at times dreary it's not worth giving up.
I think this song is definitely about a person going through a deep depression, but I also think it is optimistic in that it hints that he is climbing out of his depression.
"All the fever in my brain, I'm alright now, I can even take the pain."
Meaning that despite everything, he isn't going to give up because he's learning to take the pain. Even though life is hard and at times dreary it's not worth giving up.