I could—and possibly should—just leave the subject line of this post to stand for itself, because it's self-explanatory. That would make for a rather boring entry, however; so here's why I think it happens, and why writers should really, really resist the urge to inform the world how many words they've managed to get down on paper in a given span of time.
Writing is an intensely interesting—nay, fascinating—occupation to the writer, focused as he or she is on getting those words down on paper; wrestling with character, plot, setting, and description; watching as the words mount up, take shape, coalesce, and eventually form a whole which will, it's to be hoped, find a home in print and delight readers. Unfortunately, writing is also one of the most intensely boring things it's possible to do with one's time, involving as it does shutting out the rest of the world and sitting in front of a computer for hours on end, with nothing to show for it day after day other than a Word file which keeps increasing in size. In days gone by one could point to a rapidly-filling notebook, or a satisfyingly thick sheaf of papers; clicking on 'word count' before saving the file isn't quite as tangible or satisfactory an equivalent.
Thus it is, I think, that many writers—upon checking the day's word count—like to post the result for all to see, as if in validation: 'Look, I did accomplish something!' When I see these posts sprouting all over my Facebook wall—and as I have a lot of writer friends, they appear with monotonous regularity—I think 'Why?' I have friends who are teachers, principals, nurses, accountants, directors, waitresses, office workers; friends who work in sales, advertising, and PR; and none of them seem compelled to share the details of their working life in quite the same way writers do. Principals don't say how many in-school suspensions they handed out today; nurses don't inform us how many pills they dispensed; directors don't tell how many feet of film they managed to shoot; accountants don't tot up and then post how much in taxes they saved their clients. They know what they did, during the course of their daily round; they simply don't seem to feel the need to share it the way writers do.
It could be argued that for most people who write, writing isn't their full-time occupation; it's not a hobby, not exactly, but it isn't what they do to put food on the table. This is an even greater reason to not over-share. It's bad enough telling me how many words you got down on paper when that's what you do for a living; somehow it's worse when you're telling me how many words you wrote during your spare time. Would you be telling us how many rows of knitting you managed to finish after you'd eaten supper and cleared up the dishes? I doubt it.
The truth is, only your mother and your editor care how many words you wrote during the day; and I hate to be the one who tells you this, but your mother is lying. (She's the one who told you your first-grade paintings were wonderful, remember? Unless you grew up to be Tom Thomson or Emily Carr, she was lying then too.) And your editor only cares if those 3000 words you wrote today would make Nabokov weep in joy and admiration. Odds are good that they wouldn't. Because whenever one of those 'I wrote xxx words today' posts crops up, I know that the writer is talking about raw text in a file; there's probably been little polishing, or editing, so anywhere from 25% on up of those words will not see the light of day, and what's left may end up in radically different form by the time the work is published. Yes, good for you, 3000 words in a day is great; but let me know when those 3000 words are actually publishable, and I'll be more impressed.
It bears saying here: quantity does not equal quality. I'd be more impressed if that 'I wrote 3000 words today' post was followed up by one reading 'I chopped 500, my editor chopped a further 800, I rewrote 1200, and then realised that a key piece of dialogue had to be moved to earlier in the story to help it make sense.'
And I beseech you, in the bowels of the Lord, to not invoke any sort of Muse when talking about your writing. It sounds mildly twee at best, pretentious and pompous at worst, particularly when most writers aren't trying to do very much more than tell a decent story in a way that makes readers want to keep turning the page. Invoking the Muse for this process—particularly when self-aggrandisement, of the worst 'Look at me, I'm doing Important Work here!' sort lies millimeters below the surface—is rather like someone preparing Kraft Dinner and invoking the spirit of Escoffier while doing so. Whenever someone talks about being inspired by his or her Muse, I think of the Julian and Sandy skit from the BBC radio series Round the Horne in which they're running a film company called Bona Prods, and talking to Kenneth Horne about their latest production, a Biblical epic based on the story of Samson and Delilah. As Horne listens, Sandy encourages Julian to tell them about his idea for the screenplay: 'He's about to create. Look at his features; they're tortured. He's getting all worked up. Look, the Muse—the Muse is fluttering about, looking for a place to perch. There she is! Go it, girl! She's lighted on his shoulder!'
Whatever you write during the course of the day is between you and your computer. It may never see the light of day; if it does, it may bear little relation to those words you tallied up and broadcast so loudly weeks, months, or years earlier. By all means enjoy your writing, be proud of it, and feel free to let the world know when and where your words can be read. Until then, however, how many words you've written in a day is something best kept between you and your computer. And your editor, perhaps. But not your Mom. Trust me; she doesn't really want to know.