Being a writer is pretty brutal. Even the good reviews might contain comments that feel like arrows piercing your innards. That's why, as the author, you've got to be the toughest person in the room when it comes to your own story. Before you present it, you've got to cut it into usable slices your audience can digest. Just how adept are you at carving up your story?
I'm referring to editing techniques, of course, but I'm doing it in a colorful way (I hope). You have to be a real killer when it comes to your own story lines and plot. Too many sub-plots muck up a story, and over-long descriptions get skipped.
Length is a factor in each and every single book, and it's a problem that only goes one of two ways: the book is too short, or too long. Rarely is the length ever "just right," because if a story is really good then readers want more of it. But books can be too long as well. In fact, this is a very common characteristic among new authors who have written only one or just a few books.
Sometimes, that book your writing isn't an epic story...it's an epic length. It's never a good idea to throw a bunch of extra stuff into a story. Take care with any scenes that take readers away from the main plot. I'm not a huge fan of flashbacks, diary entries or stories-within-stories when it comes to the body of the book itself. When used sparingly they can be powerful, but if any of these elements are over-done your book could easily feel like it's dragging.
You have to be ready to carve up that book of yours, and cut it down to just the main plot. Sometimes, this is an incredibly painful experience. I would know, because I have a few manuscripts that deserve a brutal chopping and I'm fully capable of avoiding them indefinitely. But if you really want to get that book out there for the public, you have to go through that process.
Cut out any scenes that don't drive the main plot forward, or reveal some integral piece of information about a character. Every single sentence of your book should meet some specific goal that you have for the story -- it paints the picture, it moves the action, it reveals a character's inner motivations. Every word has to do something, and every scene has to serve a specific function. If you can identify scenes and paragraphs and sentences that don't do this, cut them.
Be brutal with your book and yourself. At times editing big chunks of text will feel a little bit like taking a knife to your own heart, but remember that you're serving a greater good. You're creating a better story that's easier to read. So cut out those flowery passages, the windy monologues, the pages of descriptions of oak trees that I don't really need to read, and carve up your story. Isn't today the perfect day to inflict a little damage?