Terry Pratchett is said to have written a mere four hundred or so words a day, but consistently so, and that helped him produce dozens of books in his lifetime. For a long time, my goal has been a thousand words — a little more than half that — but this has not been a hard limit. If I couldn't produce a thousand, I'd produce five hundred. If not five hundred, then three hundred. Something was always better than nothing.
You don't have to pump out a novel a week to be "productive". You just have to be able to sit down for a few minutes a day and do something to turn the wheel a little. Sometimes that wheel turns a few more times, sometimes it only turns once. As long as it turns, that's what matters.
I think one of the less-analyzed aspects of the way creativity has been commodified is the way it's been turned into its own perverse work ethic. That is, there's the wrong kind of emphasis on the output vs. the habits. People who don't know much about creativity (and unfortunately that includes most people who consume creative product of one kind or another) conflate volume of output with creative power. They're impressed by someone who writes dozens of thousand-plus page epics, because that kind of success story is easy to grasp and quantify. One-hit wonders with their own lessons, or people who squeeze out a book between stints of real life, look unfairly shabby in comparison. That, in turn, breeds creators who go looking for such urges to satisfy, whether or not they realize it.
Everyone's creative output needs to be balanced against, well, all the other things in their life: how much spare time they can devote to it; how many other resources they can use to enrich it (e.g., how much money to spend on books for research); how significant it is in their life compared to other things. Writing was important enough to me that I gave up a fair number of other things in my life to make the room I felt I needed for it. But I still make time for the things that, without which, I don't have much of a life to fuel my work in the first place.