This is about achievable goals, too. Maybe if writing is the only thing you’re responsible for doing, a higher number like 2,000 words is a more achievable goal.
But most of us also have to work, manage child care, go to school, manage a disability, do household chores, provide care for a loved one, manage a social calendar, prepare meals, etc. (most of us have several things on the list to deal with, and if your responsibilities aren’t on this list they’re still valid.)
Tolkien had meals prepared for him at home and at work. He only “worked” at the bare minimum as a tenured professor, and actively tried to get his students to drop his classes so that he could spend more time writing. His wife managed all of the child care on her own. Their household staff managed the chores.
None of us have the luxury of fucking off at work to get in another 500 words or so. (I mean, if you do, go for it! Boss makes a dollar, I make a dime etc.) We have laundry and dishes and commuting, after a stressful day of work.
So go for 100 words. Go for 50. If you find yourself consistently writing more than that, gently “up” the number. Maybe it’s not a number goal to reach at all; maybe it’s “one conversation” or “start a chapter.”
Or maybe you do it the other way around! Just write. When you feel like you’ve reached a satisfying quantity, look at how many words you wrote and track that number. This method will help you find that sweet sweet “average number of words”, which might actually be the way other authors track their work, too. Maybe when someone says, “I write 1,000 words a day” they mean it averages out to a thousand.
if you’re clever about it, you may be able to track what circumstances maximize your output. You can also see where you might struggle.
“Oh, man; I’ve got this big block I need to get done. Ah, it looks like I don’t ever get much written on Sunday nights, only 50 words or so. I wonder why? Thursday afternoons are when I get the most done. It must be because that’s my half-day at work. Huh. I’ll save the big block for Thursday.”