To me this song is very pertinent in a lot of respects at this very moment. It is a guy singing about someone that he's very much in love with that has moved on. Where he has not. Remembering where she sat not all that long ago, but tonight it's a lonely ride instead. It then turns darker and he's imagining her going on with her life while he's stuck in the past, all by himself. Every time he goes through this scenario it rips out another part of him so in essence she's taking a piece of him each time he goes through it in his mind again. The MOST emphatic line in the whole song is after the last, "and I need you". " And this last mile I travel with you", because he can't take it any longer. All his pieces are gone so he's imagining her beside him as can't stand the anguish, and ends it all, with her by his side in his mind at least.