Anyone can write every day. It's not difficult. You just have to sit down and do it. A few hundred words -- it's easy. There is no reason why anyone here can't find that much time to work on material.
But it's not what everyone should do. There is no rule that says you can't be a published writer if you don't work every single day. I know many published authors who take time off, either in huge chunks or a month or so, or a few days a week. Writing every day is not the sign of a successful author. It's a choice, and there are other choices that will work just as well.
But the real goal is to finish your work. It doesn't matter how long it takes you as long as you do the best you can with it. Some of us write more than others; that is not a sign of talent, just that we have more time to write and really don't want to do other things. (grin)
However, I'd like to make a related point on the subject. It's very difficult to finish something if you wait for the Muse or inspiration or the right mood to hit before you work on it. I've noticed a couple of things about people who wait for inspiration to strike. They have more problems with writer's block, which I attribute to waiting for the Muse to get them unstuck rather than actively working to unstick themselves. They don't grow in their writing very quickly because they don't write very often, again, because they're waiting for that Muse to strike.
A member at FM once asked me if it would be possible for a writer who can't write every day, but has to wait for inspiration, to have a career. I told him that I worked that way for years because writing was a fun break from being a mom. When I decided I wanted to be a published writer, I changed my approach because it's unlikely I could have a career writing as infrequently as the Muse showed up, especially if I want to earn a living from my writing. I wondered how he planned to meet contract deadlines if he's sitting around waiting for the Muse to drop a story in his brain. The writers I know who are paid for their work tend to follow the maxim I quote in my signature on Forward Motion:
"Inspiration is for amateurs. The rest of us just get up and go to work." --artist Chuck CloseThat's not to say they're never inspired. They are, and more often than those who wait for the Muse. The process of writing primes your mind to be open to inspiration. One fear I had when I started this blog was that I'd run out of things to write about. So far, I haven't written about everything on my list, and the list keeps growing. Because I'm writing regularly, I'm thinking about writing. When a potential topic passes through my mind, I recognize it as a potential topic to add to my list.
If Zette's right, you don't have to write every single day, and if I'm right, inspiration happens more when you're writing than when you're not. How often should you write? It's up to you, but I recommend setting a regular schedule. It doesn't have to be a 9-5 workday, like so many dreaded day jobs. But it can be, if that's the best schedule for you. You can write every Monday, Wednesday, and Friday at 7 pm. Or during your coffee breaks or lunch hour in your day job. The point is to make writing appointments and keep them.
When you know you're going to write at whatever time is on your calendar, your mind prepares itself to write during that time. That's one reason the pros get more inspiration. They've trained their minds to be ready to work during their writing time. It's been my experience that if I have a day when I get stuck, I figure out how to get unstuck much faster if I report to work as scheduled. First I try brainstorming using my favorite brainstorming tool, Inspiration. If that doesn't get me unstuck, I'll use the time to stare at the walls and think about it. If that doesn't get me unstuck, I'll let my backbrain work on it, while I work on something else. No matter which approach I'm using, I show up at my desk at the appointed time. I've noticed that my writing is the better for having a regular schedule.