I'm lucky. My day job, being a grad student in English Lit, matches really well with being a writer. And I like that day job. It means that I get paid to think about what interests me, to research what I love and tell other people why I think it's cool, and to read books. Which, you know, doesn't suck. And writing fiction means that, if I'm lucky, someday I will get to make my living by making things up.
But both of those things are still jobs, and some days, most days, actually, are not 3000 word days. Some days, thankfully rare ones, the words don't come at all. I've got my tricks: I clean the house, or bake something. I go for a run. Since I tend to soundtrack my writing, I put on the CD or the playlist that goes with that project. Sometimes one of those things is enough. Sometimes none of them help.
In those instances, I try to work on something else. I've learned the hard way that I do much better when I have multiple projects going, because it's very rare that I'm blocked on everything, all at once. But occasionally I have been, and it's terrible. Because then all I can do is wait, and hope something happens.
And so I've learned that I can no longer take days off, not on purpose anyway. I carry a notebook everywhere, and if I wake up at 4:37 am with a new line of dialogue in my head, I get up and go write it down. And the words get written, and the stories get told.