Whoever said the "little darlings" quotation (I see online that is has been attributed to many authors over the years), had it right. As a writer you must be merciless when it comes to editing. I know that sounds a bit bloody, but it's true. You must be willing to cut out the parts (no matter how proud of your writing you may be) that don't serve the story. That awesome metaphor, that cool scene, that great piece of world building - if they don't serve the story, they gotta go.
I've been struggling with this recently. I had been massaging my rough draft and working it and reworking it but I just wasn't satisfied with how TST was turing out. The draft had a lot of cool parts but it wasn't hanging together as a whole. So, about two weeks ago, I got rid of the last two thirds of the book. Yup. Two thirds. I kept the beginning and have started over again. After a moment or two of kicking myself, I feel good about it. That two thirds will reappear in some other work in some other form. I'll use similar imagery and similar scenes in my next work most likely but they didn't fit in TST. So, they're gone. They're gone and I'm free to develop the story as it should be developed instead of trying to shoe horn in those cool parts.
Needless to say, TST (which will be known by a different as yet unchosen title when it's released) will be come out not this month but a few months down the line. When it does come it, it will be a far better book than what I had ready a few months back.
Because I killed stuff.