Lyric discussion by penguinTUX 

Cover art for Big Black Coffin lyrics by Peter Bjorn and John

Since no one has tried to decipher what this song means, I guess I will give it a shot...

This song is about the guy that was dumped by the other person. He really liked her, but she didnt like him.

"it's coming back to things you've said to me i'm hiding away from reality denying myself for the better parts and you slip back and say "don't take it hard"

He is reflecting on the past and not allowing himself to recover from the past.

I also think when the big black coffin is mentioned, it is symbolism for all things black (Things bad or bad moments from the past) will be buried, like a coffin. Forgotten, as some would say.

The "Bye Bye Bye" part at the end is stating that the guy is saying bye to all the things from the past and is moving on.

I hope some people will add to what I have said.