Some days it’s not about how many words you write but about what you figure out about a character or a story. You have some new twist to the story that comes out of what you’ve been writing or you discover an aspect of your character you hadn’t seen before, something that seems to open up other possibilities. This is a good day.
I think writers sometimes get too caught up in word count. I don’t ever count the words. I do write every morning at roughly the same time. I try to write for a few hours but some days that’s not possible. Other days, especially in the summer when I’m off from teaching, I may write for more than a few hours. That daily habit has been really important to me. It keeps me involved in the story and it keeps the story moving forward. Some days I write crap and some days I write very little and some days it goes so well it’s hard to stop. But I’m there ever day regardless of how it goes. That’s what works for me.