I believe in this song the writer is telling the story about a relationship he was in while his band was on the virge of becoming big. In the first verse he talks about how he felt when the band first started, how he didn't feel like it would end up becoming big and would fill the empty space it occupied for very long, but the band kept performing despite thinking that they would just be performing as a hobby. He talks about how he didn't know how to describe where their band was heading, but it had became such a big part of his life that he didn't know what he would do without it. While he was in the band he was dating a girl that, to him, knew what was best and he always let himself be controlled by her opinion. He was in love with this girl and he would have to choose between her and the band, but he realized if it got to the point where the band would start touring, being with her would be enough to outweigh the feeling he gets from performing, which becomes the one thing that they fight about. In the chorus, it's him comparing him and his girlfriends fights to a song and how he's fed up with it to the point where he wants to stop playing it and end the relationship. She says he's wrong for choosing the band over her, but he knows that when he's performing, everything they had before didn't matter anymore. In the second verse, he talks about how he was thinking about quitting the band for his girlfriend. He feels like he's kicking an addiction. After a little while of not being able to practice/perform with his friends in the band, he's starting to miss them and doesn't know how to tell them that he's choosing his girl over the band. He waits it out a bit to think it out, when he has a conversation with his father who tells him that he can't pass up the opportunity that he has with this band and to take the luck that's being thrown out at him. He thinks some more and decides that the band is too important to throw away for love. His girlfriend decides it's time for her to leave him prematurely since she's choosing the band over her. They have a big fight as he comes home to her packing her bags. He tells her that if she's going to leave that she's going to have to face the fact that she's leaving him over something that could change his life forever. So basically, the writer is taking an opportunity with this band that'll be life changing for him and his girlfriend leaves him because she can't deal with being left in the rearview mirror.