Writing Through a Headache

I have had a sinus headache since about 3 a.m. It's one of those headaches that hangs around in my forehead and nose and never quite goes away until it is good and ready. I am guessing it will be sometime this afternoon. But I don't want to waste a morning when I want to be writing. I have enough writing projects that I should be able to find one that I can work on through a headache. I don't think I have the energy to tackle the major revisions I want to do on my sequel/prequel to The Gate House. My other Nara story, Nara of the Islands, is almost finished, but an ending is hard to write with a headache. I love writing book reviews, and I have one I need to work on for Suspense Magazine. That's a "maybe" project. But for writing fun and relaxing, I think I will go back to what I call "My Real Story." This is a story I started writing just for fun a few years ago. I have abandoned it and returned to it several times. I don't know if it will ever be something I will want published. It is essentially a fantasy story, and I enjoy wandering around in this other world when I need a break from writing "work." For me, this story is play. I am not following an outline. I don't have any particular market in mind. I have no audience except myself. The story is set in the land of Three Rivers, so named because I worked in Tres Rios when I lived in Costa Rica. The land of Three Rivers is a place of pure imagination, and it's all mine. How do you handle those days when your energy for writing is just not there, but you don't want to miss your writing time?