<Instead of thinking out of the box, get rid of the box>
What happens when we get rid of the box? I can see some panicked faces already. Don't worry the box wasn't important anyway.
To be truly unique as writers we must, we must, we must, get rid of the box. Be out of the ordinary from out of the ordinary. Don't be like all those writers who say they aren't like those "other" writers. (I don't have any more of those cliches; you're safe for now). So what if the essence of your novel has been done a million times over. It's the details that make it YOUR novel. It's YOUR writing style that make it different. Take a little risk. Do something spontaneous! This is a call to action! Just kidding.
You don't need to lose yourself or your novel to changes you make to the story. But you do need to make it shine in a way only you can, differently than those other writers. Make sense? Good.
Keep your pen up!