What happens if you're writing along, loving it, and then you miss a day or two, or three, or four and you find yourself slightly bored with the thought of picking up the pen or opening the folder?
This happened to me while I was writing my first book. I put it away for weeks at a time, sometimes months, and it took me five years to write a book that ended up being just under 200 pages long. Kinda lame, yes. I got bored with it, I listened to the inner voices that told me I was wasting my time...
Well, I've since discovered some things that will help. If you do need to put the book away for a small amount of time to take a breather, fine. Do just that. But don't NOT write something else every day. Keep your writing habit alive by still writing/journaling/scribbling something down each day. We must ingrain the daily writing habit, even if it's only ten minutes at a time.
Another idea might be to try a fresh project for a bit and then go back to the original one that was giving you fits. When you get a little bit of distance from it, sometimes you can see the thing that was wrong, or you realize you really do like that idea and you're willing to work with it again. I don't suggest you put it away for five years, though, if you can help it.
Maybe it would help to brainstorm a list of possibilities for your characters. Start making a list of things that could happen to him/her. Raise the stakes! Do something horrible and let the character work her way out of it. Shake it up a bit.
Go for a walk and think about your book. Let the fresh air slip into your head and rejuvenate those tired brain cells. (Or something like that). Truly, sometimes just moving around does wonders for my writing abilities.
Sit somewhere crowded and listen to people talking. See if there's anything you overhear that might be useful in your story. Challenge yourself- see if you can find a way to fit in something you might not have thought of otherwise.
Don't give in to boredom or writer's block! Fight it!!