As much as writers might want to keep going every day, there invariably comes times where one doesn't know where a project is going. In his previous rule, Masello gave advice on how to keep writing every day. But with this rule, he acknowledges that there are times when whatever trick a writer tries just isn't going to work. Even regular work habits might not be enough to keep the ball rolling.
And when that happens, Masello says, take a break. Step away from your work for a while. Taking some time off might give you a better perspective on the problem that's facing you. And doing other things will give "the well of unconscious cerebration" (Masello quotes Henry James here) a chance to refill.
Now, on the one hand, this advice may seem contradictory. Is Masello saying stick to your desk, because that'll work, except when it doesn't?
But on the other hand, I'd say it's more of a question of learning your own writing habits. Don't just sit at your computer for a minute and throw your hands up in exasperation when you don't know where the story is going. Learn to recognize your own writing moods, so you know for sure whether your current problem is one that requires sticking to the desk or requires taking that walk in the park.
Take me as an example. (Digression: I know I do this fairly frequently, but that's only because of all the writers in the world, the one whose habits I'm most familiar with is me.) I often spout the standard advice that if you want to be a writer, you should make a point of writing every day. I really do believe in that advice. And when I find myself in the middle of a project, I do my best to stick to that advice as well as I can. But, to be honest, there are also stretches of time in my life when I don't get as much writing done. And I've come to realize that maybe I do need to take some time to let the well refill.
However, I don't just give up during those stretches. Instead, I sit down and try to write something anyway, to get a feel for whether or not I'm really in a "need to let the well refill" state. If I am, I recognize it because...well, because of something I can't define. But I know it when I feel it. And so I step away from the story, and continue to let the well refill. But, most importantly, I'm not just giving up. I'm making sure that I really need to take that break before I actually do it.
So I think Masello is actually saying that we need to learn to recognize and work with our own writing moods. And to be realistic about when we really do need to take that break.