The first draft is the toughest to complete. For the majority of potential authors, they never complete their initial novel first draft.

As a novelist, one should focus on getting the basics of the story out and on the page. Most folks keep going back over their work, self-editing themselves into a standstill. This is the wrong step to take, since editing uses a different hemisphere of the brain, and switching between editing and writing is the equivalent to putting your car's automatic transmission in forward and then into reverse while the car is in motion.

One of the reasons I like NaNoWriMo is that it forces people to keep moving forward. It turns off that annoying editor in your head so you can vomit forth the story. Make no bones about it, a first draft will always be shit. The only way to make it a salable work is to polish that turd until it turns into a diamond.

To complete your first draft, focus on getting your words down as fast as you can type. If you come up with an idea that is perfect for three chapters back, just make a note and continue forward. Changes come with the revision process. I normally put notes to myself in curly braces {like this}, so I can dig them out with the search function when it's time to get to the revisions.