When you're writing a book and you suddenly find that you've got 78 chapters and nary a resolution to a thing, much less have yet to introduce key elements, you're in deep, deep trouble. The story that you have set out to tell is so mired in sub-plots and multiple characters that you can't really recall the resolution that you'd dreamed up, so you just keep adding until it "feels" finished, as opposed to actually being finished, but you just have this one thing to add then it'll be perfect! You have this brilliant idea and some background to go along, and you're stoked. You sit down, and start writing, and things just take on a life of their own and...OK, stop writing right now.
The first thing that you have to learn how practice as a writer is self-control. Yes, you can tell the tale however you deem fit, that is your right as the author. However, it is the right of the reader to not even give your book a chance because you just keep traversing from place to place without ever really getting to the meat of the story! The beauty of your craft is lost if your reader can't manage to follow your own plot lines or narrative arcs. Being ambitious is one thing, but if you fail to create and follow even a single storyline down to a conclusion, you're not doing anyone any favors. Remember those tedious storyboards or character studies you had to create in horrible detail during creative writing 101? Yeah, they actually serve a really useful purpose - to help hone your instincts for focus. You don't want to do those? Fine with me. At least jot down a simple outline to keep you on track, ok? No, you don't want to even do that? Ok...But that means that you must learn to turn a critical eye to your tale and learn when to cut out the truly meaningless wanderings of your mind. You may have created this beautifully masterful description of (insert that something here), but if it doesn't do anything to further your story, it may actually be lovely yet ultimately useless gunk that could be flushed out during your own re-read.
Wait, what? You don't re-read your own book before you send it...anywhere? That may actually send me into a swoon. Seriously, if you don't want to take the time to read it before it leaves your hands, then why should I be bothered to take the time to read it, ever? THIS SHOULD NEVER, EVER, EVER HAPPEN! Oh, goodness, I'm shouting. Sorry about that. But for the love of all that is good and right in the world, re-read your story before you send it. To anyone for any purpose. I don't want to be forced to shout at you, but this is important. This is something that I shouldn't even have to put into words, frankly, but I find that I must because people have such high opinions of their own craftiness that they actually do just write and send. Please don't have a writer ego that needs such a tremendous beat-down. I don't want to break out the flying monkeys, but I will, if you make me. Write. Read. Put down for a bit. Re-read. Then, if you're happy with it, send it off. This is elementary, my dear author. I will be forced to take the element of fire to your feet if you fail to re-read your own work. Along with the flying monkeys. Then it would really suck to be you.
Shouting *and* threats? Goodness, me, I'm getting cranky in my old age.
Finally, consider of the back cover of your book. Really visualize it. If you can't write up a synopsis in less than a page, you're going to need an editor with balls of steel to contend with that sort of thing. To me, a gigantic synopsis indicates a failure to recognize the key points of your own story and if you can't manage it, it's time to seriously cut down on the plots (or characters or ideas) that you're trying to write about. Seriously, if you want to touch on that many twists and turns and people, perhaps envisage a trilogy or something, where the whole of each arc can be given equal due. If your synopsis isn't choice then the chances of your book rambling and shambling on it's own merry way without regard is high. You owe it to the story to tell it in the best way possible. Words are your own chosen currency, spend them wisely.
Focus is your responsibility, as the shepherd of your story, to apply to your book liberally. Your editor will thank you. Your readers will thank you. The flying monkeys might thank you, too.