When you started out, it was glorious. You had a clear idea of what you wanted to achieve, and a boatload of momentum. You were rattling off paragraph after paragraph with ease. It felt like nothing could stop you. But something did. At some point, you ran into something, some factor, be it external or internal, that caused your progress to slow to a dead stop.
It's time to accept you've run into a block and refocus. These guidelines should give you a fresh perspective on your work. You'll emerge from the other side of that block revitalized, with a better understanding of what caused your difficulties, and a much greater chance of success.
Think Big. Start Small
You started off like a steam train, but now even short sentences are painful to extract. How can you get past this seemingly insurmountable block?
Rethink, refocus and retarget. Start off with a relatively unambitious daily goal, something like 300-500 words. It may not seem like much, but 300 words is better than ten words...or no words at all. Before long, you will be consistently smashing that target, motivation fully rejuvenated. After that, feel free to adjust your goals accordingly, and don't be afraid to adjust that target downwards if you start to struggle again.
Know Where You're Going
Some people have the ability write to directly from the heart with no particular idea of where their story is going or where it will end. Legendary horror writer Stephen King has often said he starts with nothing but the kernel of an idea, and simply runs with it.
But in most cases, even for gifted writers, it is much more sensible to have an idea where your story is going. This approach is much better for guarding against those lapses in concentration that come about by not knowing where to go next with the story.
Outline your novel, each and ever story beat, and have a clear beginning, middle and ending in mind. Things will probably change along the way, but with this strategy, you should never be stuck for something to write. Knowing where you're going is half the battle.
Choose a Unique Place To Write
The best place to write is your favorite place to write. Writing here will feel more comfortable, and if when you're more comfortable, you're likely to get more done.
Create a special place, somewhere totally dedicated to your pursuit, where the only thing you do in it is write. By the time you've used this place a few times, the effect should be like a form of conditioning, and even just entering your special area should have the effect of mentally preparing you to work.
Give Yourself Weekly Deadlines.
Something to work towards is always better than working in a directionless vacuum. As previously mentioned, as long as you keep your targets modest and achievable, they will help you make progress.
Give yourself a target for the end of the week, be it a total number of words, the end of a chapter, or a percentage progress -- whatever goal works for you. And be happy when you beat the target. Allow yourself a little celebration. But likewise, hold yourself accountable if you cannot reach that target. Be strict. You'll thank yourself for it later.
Many respected authorities on writing will tell you that you should keep your own council, only revealing your creation towards the end of the process, allowing the purity of your vision to form fully before any outside influence.
The problem with this approach is that any huge problems you haven't noticed because you're too close to your work will go unnoticed. That massive, continuity-breaking plot-hole that has gone overlooked for six months will be much harder to address once the whole thing is complete.
Get some perspective on your work, and try not to be too precious about the feedback you receive. If you've selected your confidant with care, any criticism you receive will be constructive and will increase your chances of being published. Unless you're incredibly talented or insanely lucky, the only feedback you're likely to receive from a publisher is a rejection letter. Which is much less constructive.
Writing is hard. Be under no illusion to the contrary. And when you're writing a long-form project like a novel, that difficulty reaches its peak. But, with these strategies, a bit of talent, and no small amount of tenacity, there's no reason why yours can't be one of the 3% of novels that actually reaches completion. Now wouldn't that be fantastic?