First of all - I do not know the Twilight movies, so I'm free of any connections to this.
The song seems to me like talking about doing something for a very long time ("and the days will come and go/and the band will march along"), perhaps some kind of job or something, you really don't like or that doesn't fit your personality, until it actually changes you into something you weren't before and perhaps never wanted to be.
First of all - I do not know the Twilight movies, so I'm free of any connections to this.
The song seems to me like talking about doing something for a very long time ("and the days will come and go/and the band will march along"), perhaps some kind of job or something, you really don't like or that doesn't fit your personality, until it actually changes you into something you weren't before and perhaps never wanted to be.