For some people, writing 10,000 words is easy. Heck, for some writers I know, writing 40,000+ in one marathon writing session isn't unheard of. But for me, even 1,000-word days aren't common, because I'm a painfully slow writer. Sometimes, 100 words can take hours (and that's not counting the editing to come).
This isn't because of the ever-elusive notion of inspiration, though of course it can be easier to write if I know what will happen next, what the scene should look like. If I don't have to do research as I go to make sure that what I'm writing in my contemporary (i.e. real-world) story could reasonably happen.
Slower writers are at a disadvantage in today's publishing landscape, where the #1 piece of advice is to keep putting new work out—and often—to keep readers' attention, maximize marketing opportunities, etc. If you aren't on par with authors such as George R. R. Martin, you just don't have the luxury of waiting years between books. Even traditionally published authors try to write more than one series or genre with different houses, specifically so that they can publish more often than the traditional pace of no more than one book a year.
Sometimes as I write, or more accurately sit struggling to write the next line, I remind myself that I ultimately make up a lot of the time in the editing process. Faster writers often need more intense revisions because their drafting method is of the "get words on the page, any words, good, bad or ugly, just do it" style. To be clear, it's great that that works for them. It's an element of my own writing too sometimes, to a lesser extent. But ultimately, that's just not my writing style.
Of course, my first drafts are still pretty terrible. Just ask my critique group (who don't see my very first draft anyway, but you get the point). But, they're usually readable and more or less coherent. You can see what the story is at its core, where it's going, who the characters are, etc. I have never had to delete entire subplots or add new ones, or finish out ones that started and went nowhere. I don't tend to add new characters, or delete ones either—not because I plan things out before I start writing, but because I think things through carefully as I go, even when the story veers somewhere I didn't expect. Ultimately, all of that slows down the writing itself, and forcing that word count up bit by bit can be draining, and disheartening.
And I know I'm not alone, being a slow writer in this fast-paced new wave of publishing. More experienced authors have even offered workshops on how to balance all those reader expectations and marketing opportunities with being a "slow" content creator. Even Kafka struggled, as this photo I recently came across shows:
All that to say, I know it's been a while since my last book came out, and meanwhile I haven't even announced a release date for the next one. But I personally can't write them any faster than I do. And I hope you'll find the wait worth it.