Writers' Fatigue / Self-Imposed Deadline

I have this story I'm writing, called "The Dream Machine."  It's going to be a full-length science fiction book, a genre that I've never seriously attempted to write before.  I'm interested in the story, but something is bogging me down:  Writers' fatigue.

Writers' fatigue sometimes happens during the writing process, and for me, it's almost brought my creative process to a complete standstill.  I've looked online for remedies to this problem, but nothing seems to be helping.

That brings me to my next point:  My self-imposed deadline for the completion of my book.  I've been telling the online community (that's you guys and gals) that my book will be ready by spring of 2013.

Now, why would I do that?  When it comes to writing, I'm my own boss.  I don't answer to a publishing company or an agent, because I'm 100% independent with my writing.  With this kind of freedom, why even mention a deadline at all?  Shouldn't I just write it and release it whenever it's done?  That's what I used to think, but I've also never wrote a full-length book.  I've finished countless term papers, history reports, and essays, but never a full-length book.  What's the difference?  A deadline.

I probably announced my deadline around the middle of this year, and I'm still happy I made that choice.  It keeps my thoughts trained on writing my book, even though my fingers haven't been putting words into chapters recently.

Writers' fatigue isn't something new I'm experiencing.  It only happens when I attempt writing novel-length stories.  In the past I've even looked at pages of text on my computer, considered the time and effort it took me to accumulate the vast amount of story, and then deleted the file because I just couldn't take on the task of finishing something of that magnitude.  Was it a waste?  Not really, because I've learned to write better fiction with every attempt.  Should I have kept those stories, and tried to edit them until I was satisfied with the results?  Maybe, maybe not.

Do I want to delete "The Dream Machine," and let it join the buried remains of previous failed stories from my past?  Hell no!  I'm still trying to make the deadline, and I'm trying different things to get over the hump.  Recently, I tried some free association and came up with some new ideas.  Luckily, there weren't any huge flaws in the story, and the changes I want can be made fairly easy.  All I have to do is fine tune some things, write the copy, and get back on track.

If anyone has pointers for how they overcame writers' fatigue, or what might work for me, please let me know.  My main problem seems to stem from the vast amount of story, and how I can easily cause plot holes if I don't carefully consider the twists and turns.  Until then, have fun writing and I'll try to do the same.  I'm curious to learn about how other writers pace themselves and set goals.  How do you plan out your stories?  Do you set goals for how many words you should write?  If so, do you set your goals by the day, week, or month?  How do you review your material?  How do you get your ideas?  What do you do when you run into writers' block?  What do you do about writers' fatigue?  I'm excited to learn, so let me know.