Oates has published nearly a hundred books, so when she talks about how to keep going, it carries weight. Her most useful advice cuts straight at the excuse most writers lean on: not feeling in the mood.

The Direct Answer
Be pitiless about mood. The writing creates the mood.
She argues that waiting to feel ready is a trap, and that the act of writing itself changes your state, per her Paris Review interview.

Stop Waiting to Feel Ready

The single most quoted piece of Oates advice comes from her Paris Review interview, and it reframes the whole problem of motivation.

One must be pitiless about this matter of 'mood.' In a sense, the writing will create the mood. If art is, as I believe it to be, a genuinely transcendental function, a means by which we rise out of limited, parochial states of mind, then it should not matter very much what states of mind or emotion we are in.

Joyce Carol Oates, The Paris Review, The Art of Fiction No. 72

She backs it up with her own experience. In that same passage she says she has forced herself to begin writing when utterly exhausted, when she felt her soul as thin as a playing card, and that somehow the activity of writing changes everything. The mood follows the work. It rarely arrives first.

It's a useful thing to hear from someone with her record. The temptation, on a bad day, is to wait until you feel more like a writer. Oates's whole career argues the other way. The feeling is downstream of the doing, so the move is always to start, however thin you feel.

Protect the Work From Interruption

The other piece of advice she returns to is practical and easy to act on today. Asked what damages writing, she has said plainly that the worst thing is being interrupted, and that you have to be in some place where you're not interrupted. Her morning longhand sessions are built around exactly that kind of protected quiet.

She also keeps the bar simple once you're actually working. Her blunt rule for holding a reader, drawn from show business, is don't be boring. It pairs well with the mood advice: stop waiting to feel ready, then on the page worry about one thing, whether the work earns its keep sentence by sentence.

Put the three together and you get a working philosophy. Don't negotiate with your mood, don't let the world break your concentration, and don't bore the reader. For how she actually structures her day around those ideas, see the full Joyce Carol Oates writing routine.

What You Can Steal