This song is about how people can get so involved in their own dealings that life passes them by. The dust, worms, and spiders all signify aging and death. People have to go out there and live life to the fullest - making sure they wash up, of course.
I also don't hear anything in the song that points to it being about a relationship. It just isn't there. I do think the song is about being depressed. There are many references pointing to that in the lyrics and in the music itself.
i read that this was written after a long tour when thom stayed at home for a long time, the worms where his pets in a farm thing, and basicly describes staying in cos you feel low.