Getting back to the quote, one reason I like it is because it should motivate a writer to compose an original story, not something that mimes what has been written by another author(s). I believe it's safe to say that the best stories are those that offer a fresh and authentic expression from the writer to the reader.
Another point from taken from Ms. Morrison's comment is that if the subject is so strong within the writer, then that person is the one who needs to write the book because only she knows the content and direction of the story. You certainly don't want your novel to sound formulaic.
Another take for authors is not yielding to others (readers, editors, and moms) on changes in a draft if they feel it doesn't strengthen the novel. Only the author knows the story. It's his creation. Now don't misunderstand. I think it's good to listen to advice and contemplate what it means, but if it doesn't feel right and it's not something you want to change, delete or add, then don't do it. If you feel it's an action that you will regret later -- that gut instinct -- then don't do it. It's the author's novel, not someone else.
Until the next time....