It's common (though not universal) wisdom that a professional writer needs discipline: you can't wait around for inspiration. Writers who write every day (or lock themselves in their office for the whole weekend) are considered to be better technicians and have better outputs than those who only touch the keys when the right mood strikes.
To a certain extent, I agree with this in the sense that writing is a skill that improves with practice and the ability to write for long stretches requires endurance. It's like a muscle: the more you exercise it, the longer you can keep going.
But there's another component to the exercise metaphor: rest. Few exercise regimens recommend working out every day of the week. Instead, you might take a break two days out of the week - or more, depending on the strenuousness of the exercise. This gives your muscles a break and prevents your body from falling into a routine, which is when exercise becomes less effective.
Similarly, I believe that most people have dormant periods where they need creative rest - time away from the writing to pursue other interests. It gives your brain a break and prevents writing from feeling like a chore. A few days a week? Probably not - I tend to see this in terms of weeks and months, but everyone will be different, not everyone will have a pattern, and frequently it's a question of when and how life interrupts.
When this happens, it's about trust and self-discipline. You have to know your patterns and believe that the creative spark will come back. You also have to know when you really need a break versus simply feeling a bit lazy.
And what does one do during the breaks? Live life - and that's all fodder, after all.