From Advice to Writers:
Be ruthless about protecting writing days, i.e., do not cave in to endless requests to have “essential” and “long overdue” meetings on those days. The funny thing is that, although writing has been my actual job for several years now, I still seem to have to fight for time in which to do it. Some people do not seem to grasp that I still have to sit down in peace and write the books, apparently believing that they pop up like mushrooms without my connivance. I must therefore guard the time allotted to writing as a Hungarian Horntail guards its firstborn egg.
— J.K. ROWLING