Kids
My kids, too, have been trained from birth to never, ever interrupt when I'm writing, unless there's a fire, and the flames are nearing my office, or there's not just blood, but arterial blood, or Reba is at the door asking for me with a really passionate look in her eyes. I had such a sign on my office door for years.
I think the most valuable thing any writer can have is an office with a door on it, and the willingness to close the door, lock that door, and forbid knocking unless a true emergency takes place..
I love solitude, and going off to the cabin is something I love to do, but it isn't because of the kids or my wife. They know better than to bother me.
It's all else I want to get away from. It's the phone, the internet, the TV, the vacuum cleaner, friends, the insurance guy, the bills that come in, the checks that have to be written, anything and everything that puts a ripple in the quiet pond I'm looking for.
And going away also means you don't have to feel guilty about shutting out friends and family for a time, and friends and family do not have to feel guilty about interrupting you.