Lyric discussion by SeptemberSun 

Cover art for Heart + Soul lyrics by Black Rebel Motorcycle Club

I think poli got the meaning right, it's about telling someone you'd die for how you feel about him/her. The person in the song is probably about to give up on it all because the other one never returns his/her feelings, but this is one last call for the other one to save him/her. The selfishness (for once he/she will think about him/herself) will end his adoration for the other person, and this song is one last call to be saved. (Last chance, probably with some hope in it too) Great lyrics, great song.