When it comes to writing a novel, there are two schools of thought. One says you need to wait for inspiration before you start pounding away on the keyboard. This theory says that you'll just gargle out crap if you don't. The other says you need to gargle out crap, that you need to type away before you lose your nerve, and sort the mess out later. So, which one is it that we should follow as writers? Speaking for myself, I think it's a bit of both.
It's definitely possible to finish a novel that you're not really invested in. I've done that a few times (and only published one of them so far after many extensive edits), and later edited it over and over again until it was something I could be proud of putting my name on. It was a lot of work, but in the end I had a finished book of high quality. That being said, even books that you're writing that you absolutely love the premise of, you will get sick of writing at some point. You'll reach a section where you're not sure what should happen, or you are sure what should happen, but you don't want to have to write all the stuff that comes between your last scene and what you want to happen next. Those are instances where you'll have to enact the second method of pushing through, writing even if you don't feel like it, maybe even writing something that's not that great, knowing you'll come back and fix it later. This can be painful, but if you're writing to move the story, doing what feels right, you may not have as much work to do later as you think.
Now, there have definitely been times when the inspiration has been so strong in my stories that the books almost wrote themselves. As I stated above, this does not last in any work, you always reach a point where it gets bumpy, but some books for me (like Bad Dreams) did come easier throughout the whole process than others. One of my favorite memories of writing Bad Dreams is one that involved me waiting out my inner inspiration. I was probably 55,000-60,000 words into the book at this point, right at the end of it in terms of the story, and I knew I needed to nail the ending, but I just didn't know what that ending needed to be yet. So, I waited. thinking on it everyday, reading, talking to friends about my dilemma (I didn't share details, as I was afraid of spoiling the story) until I finally felt I was close to what I needed to do, and then I sat down and wrote it. I didn't have the full ending in my head, but I had an idea of how it should feel, and then I sat down and did the work, and it was an ending that I've received the most compliments on to this day. So, sometimes it pays to wait for your muse, as long as you're aware it may never come fully formed, and you may have to work with whatever she's willing to bring you (or "he." I hear Stephen King's muse is "a basement guy.")
In the end, no matter how you choose to fuel yourself for your writing (whether with inspiration or coffee) it will be you sitting behind the keys, pumping out words as fast and fluently as you can to build a world that didn't exist before you willed it. The choice is yours on how quickly you get there, and on how vivid that world is, but whatever you do, don't give up on that world. A story abandoned is a sad thing. It's a bicycle without a chain. A balloon without air. Push through, or take a pause and think about your story as long as it takes until you know (or at least "feel") where your story needs to go. You owe the story (and yourself) that.