I'm training to walk a half-marathon. In case you're wondering, that's 13.1 miles. The most I'd ever walked before was six miles. I figured if I could ever reach mile seven, I'd be certain to reach mile thirteen. Saturday I walked seven miles. Now how do I feel about that assumption? Seven miles is not 13.1 miles.
Finishing a novel is not so different than trying to finish a half-marathon. You start off with a big idea and much like a first short training session, your enthusiasm carries you for a while. It might last for a paragraph or a few chapters, but eventually the joy of the process turns into dread. You wonder what was so great about that original idea.
At risk of sounding like a Nike ad, this is where the tough get going. Stick with your story. How? Show up. Grab your pen. Move it around the page until your squiggles become words. They may not be the words you'll end up using, but soon the right words will be there. Just because you showed up.