You have to realize that you’re not going to be in a writing mood every day, so don’t beat yourself up when that happens. My creativity tends to come in cycles, and I’ve met a number of other artists who say the same thing. When I’m on the writing side of the cycle, I hold myself to a certain quota a day. For me, I shoot for a 1000 words a day. If I hit that, I can go to bed satisfied, if I do any more, I feel extra good about it. You should set your quota to something reasonable based on how much time you have to work, how fast you type, etc. It should be a realistic expectation; you don’t want to depress yourself by aiming too high. You might want to start out at 500 words a day, and if it seems like that’s pretty easy, try for 700, and so on (but make sure you cap it eventually). You want your quota to be somewhat challenging, but not enough to be daunting. What that number is will depend on the individual writer. Once you’ve figured out what it is, stick to it, don’t decide, “I’m going to challenge myself and try to do MORE each day this week.” Or try to play catch-up when you fall short one day. That’s how you burn yourself out. Find something comfortable, stick to it, and it will eventually become a routine. And, in meeting my quota, that doesn’t mean I write 1000 words for one particular spot. I might write a 300 word scene, then a 700 word scene to be saved and used later in the story (see: “Skip the Boring Parts”). I write what compels me at the time, and as much (or as little) as I want for a particular section— my quota is cumulative for the day, not how much was done in one sitting or for a particular spot in the book. The quota is how you keep yourself feeling like you’re accomplishing something. Your page length might not be growing much, but if you keep track of your daily word count, you’ll know you’re moving, and it’s the movement that’s important.
Similarly, give yourself time to rest. There will be a few days, or week where you just don’t feel the drive to write. That’s ok— don’t panic, it doesn’t mean you’re stalling out. When I’m not feeling up to writing, I usually will do something creative that ties into the story somehow, but doesn’t involve actually looking at the words. I might do an illustration, or write some music, or just put together a playlist for it. You could try sketch a map, or a costume, or a weapon, or maybe write a musical theme for a particular character, event or place. Or you can do some research to get further ideas or to gather details to make your story more intricate. Creativity is a bit like a muscle, you don’t always have to (and shouldn’t) exercise it in the same way; as long as you consistently use it, it will stay strong. Many times, I’ll get an awesome idea for the story when I’m not trying to write; it will come to me as I’m drawing, or working on music, or something like that. Sometimes I’ll draw something and go, “It looks a lot cooler this way” and then I’ll adjust the story just so I can use the picture.
The writing drive can also be influenced by other things that require writing. I have a harder time working on my book when I’ve had to write a lot of papers for school, or if I’ve been writing a lot of intensive e-mails or forum posts or something. It’s like the linguistic part of my brain gets tired; even though I haven’t been writing creatively, I just feel drained of words. So, it’s something to be aware of. Even though you might not be writing creatively, you could still be expending that written energy. Not to say you should avoid other writing, it just means if you feel tuckered out verbally, don’t beat yourself up. Go work in another creative medium for a while and let your words replenish.
The important thing is, don’t stress yourself. You shouldn’t go into your novel thinking you have to prove something, or that you have to make it work. Write because you want to, because you have a story to tell. Don’t worry about if it’s going to be good or worthwhile— if it’s got you excited enough to write about it, if it’s been on your mind this much, it’s worth it. And when you write, you write what you do for a reason. If you don’t know why you’ve written something a certain way, don’t doubt yourself. You can change it later if you need to do, but just try to go with the flow, especially the first time through. And don’t write thinking you’re writing a novel. You’re writing a story, it just has the potential to be a big story. Don’t worry about page numbers or the total word count; it will be finished when it’s finished.