There’s something to say (see Anne Lamott) for getting to “the end” and doing the worrying later. That way you have a completed draft behind you.
There’s also something to say for avoiding what ultimately seems so discouraging or despicable that revision resembles cleaning out the Augean Stables.
Finally, there’s something best of all to say for choosing something in-between. Why write chapters without scene goals, paragraphs without focal points, and sentences so tortured that even the author can’t decipher the meaning? Why compose an entire whole novel in passive voice while repeating, dragging out, and “telling”? Nor would it help to write so sloooowly that you lose all faith in what originally motivated you. What can you do instead?
~ Make a plan.
This might be a scene goal outline, a storyboard where you write whatever scene turns you on that day, character arcs for everyone important, or even an old-fashioned outline. It doesn’t matter what plan you choose or whether you later change it radically. It only exists to help you produce prose neither ghastly nor too polished for your first stab.
~ Keep a schedule.
Life, as they say, happens. Accidents, birthdays, trouble coming in threes, flu, migraine, date night, and so on. Why pretend that you won’t have dozens of reasons to prevent churning out pages? Create a reasonable, realistic commitment, i.e. x hours a week or y hours a day. Then you won’t have to pretend.
~ Advance both the plot and the number of pages.
It won’t help to have thirty exquisite pages if they’re all you’ll have for the next few years. If your time is precious, don’t squander it reworking material that you’ll change after you know your characters and their journey—because your first draft is done. Don’t proceed as if you know nothing about how novels work. Also don’t proceed as if you must immediately accomplish everything you know about how novels work.
~ Follow the dream.
Write this book because you love it. If you don’t, maybe you’d rather find a better day job instead. Feed the dream. Don’t starve it by worrying about everything you’ll have to fix. Productivity and passion blend beautifully. Negativity and passion do not.
~ Decide what a strong first draft means to you.
If you can define that without rationalizing, you’ll know just what you need, how much revising you should do right now, how much later. Only you know how good is “good enough.” Set the standard. Follow it, even if you’re having a wildly bad—or good—day.
Tip: You know your process better than anyone. Honor it, but get the first draft done.