This song seems to indeed be about illness or, more specifically, getting older and the slow march towards death. These are the thoughts of someone near the end. From here you can almost see the sea = from here, I'm not far from heaven, I'm not far from the afterlife.\
A piece of cardboard taped to where the windowpane used to be seems to be a reference to someone in the hospital, being held together when their body clearly wants to give out. This person is "another fool in the line", waiting to die and move on to the afterlife.
"Here comes the cavalry" = death is coming soon, to save the narrator from the pain they're currently in.
This song seems to indeed be about illness or, more specifically, getting older and the slow march towards death. These are the thoughts of someone near the end. From here you can almost see the sea = from here, I'm not far from heaven, I'm not far from the afterlife.\
A piece of cardboard taped to where the windowpane used to be seems to be a reference to someone in the hospital, being held together when their body clearly wants to give out. This person is "another fool in the line", waiting to die and move on to the afterlife.
"Here comes the cavalry" = death is coming soon, to save the narrator from the pain they're currently in.