The answer is messy and convoluted . . . pretty much like the writer brain is.
I don't think I've ever gotten sick of writing during the drafting phase. Sure, I've stressed myself out during it, trying to get it done or worrying that the story won't turn out right, or that maybe this is the time I'll fail at writing a whole book.
But as for actually getting sick of writing?
Absolutely not. Drafting and the initial stages of revision are the best part of this gig. Drafting is when you're in the act of creation. It makes me alive inside. I love hanging out with my characters and watching them do their thing. Generally speaking, the happiest seasons I experience are the ones in which I'm regularly drafting. (I think my family prefers me then too.)
Took me awhile to figure that out, though. I'd get into a slump and hate the whole darn writing thing: it had become work.
The slump would generally hit after revising a manuscript headed to press for the three thousandth time and proofing it for the eightieth. A slump hangs around after doing rounds and rounds of book signings and other promotional stuff. Basically it's when you want to torch your new book because you're so close to it that you can't see it objectively anymore and you're sure it's garbage, and it's been months and months since you wrote anything new.
At the darkest, most depressing part of the slump, I'd begin a new project . . . and discover the magic all over again. It happens every time: the sun comes out, I'm energized, and I love what I do, eager to get back to the book as soon as I can.
The slumps are the hard part. While they are filled with "writerly" things, they aren't what I consider writing. They hit after I've crossed the finish line of both drafting and initial revisions. I love revising (at least, at first; I hate it when it's #1,987) because I can take what's already there and make it better and better, like molding clay into the right shape.
It's when you're (or at least I'm) revising and editing it to death and can practically recite the thing in your sleep that you start to hate it, because it's no longer fresh. It's lost the magic for you.
Slumps also hit when you're so swamped with the business side of things that you don't have time for the creative stuff. The inner writer child needs the rush and excitement of creation to keep going, to not wither and die.
I haven't written anything brand new in about a year. Band of Sisters was submitted October of 2008, and shortly after that, I finished the YA folktale. So this last year, I had revisions and edits for Band of Sisters. Then I worked on revisions for the folktale. I'm currently revising my old murder mystery.
The only new writing I've done (unless you count magazine articles and blog posts, which I don't, because although I enjoy them, they aren't my first love: fiction), is for my upcoming chocolate cookbook. While that was a tasty experience, it still wasn't drafting fiction. (Honestly, my favorite part of doing that book was writing commentaries on the recipes and having fun with the manuscript on the keyboard.)
I'm glad I can recognize the problem. After enough years of the cycle, I know that what I'm feeling isn't that I hate writing, but rather that it's been too long since I drafted a new novel. I'm particularly glad that I know what the real issue is because I have so many other pots in the fire right now that, unfortunately, it'll still be a spell before I get to draft full force on anything new.
But that new book is dangling out in front of me like a carrot. Or a chocolate bar.
And I can't wait to eat it up.