I'll be honest. Most of the time, I have no idea how to answer that.
Anyone who knows me well at all (which includes very few) knows that if I had my way I'd lock myself in a cabin in the woods, with a small freezer full of home-made eggrolls and single-serve raspberry cheesecake, and not come out again. I'd turn my back on the world, all the while depending on it for royalty checks just so I could continue my hermit lifestyle. I've always heard that the most popular authors, at least in sales, are always men. Honestly, it figures. Of course they're mostly men. Someone once wrote that if you want to be a successful writer you must think about writing from the minute you wake up to the minute you go to bed.
What (relatively responsible) wife and mother could possibly do that?!
I mean trust me, it's not like I don't want to. I assure you more often than not I really, REALLY want to. The world in my head is much more interesting and lives up to my own personal expectations far better than the one I wonder around in on a daily basis. But hiding in my head is not going to get the dishes done. It's not going to get the laundry folded. And it's definitely not going to teach my children the things they need to know to be successful, and relatively well-adjusted, adults. (No matter how tempting the thought of a live-in nanny and a full-time maid is.)
So I guess that's it, isn't it? There lies your answer. You keep going, despite wanting to run for the woods with you Mac in-tow, because you have to. Because you simply can't accept not doing it. Because you are a considerate, rational person. (Mostly.) I believe that self-discipline and determination comes from having such a deep appreciation of the consequences that you feel there is no other choice. Like the diabetic who keeps strictly to a specialized diet. It's no longer a matter of will-power. You know what will happen if you don't. So you simply do.
Now, that having been said, there is an upside to this whole "living in the world" thing.
Dwight V. Swain wrote that one of the mistakes that most authors make is the idea that they can simply disappear from the world and write. The problem with that is, then where are you supposed to get your material from?
"Write what you know. And what you don't know, learn."
An author has one simple, solitary job: Experience, then share it. So get out there and live. For some of us that may mean laundry and dishes. For others it means the night-shift at the local diner. Nevertheless, go out there and seize it. Because without that every day grind, without the things we all learn from our own very personal perspective, then you'd have nothing to share. The world would never be able to see itself the way you see it through that one median you have to share it with.