I'm not a writer, but I certainly have problems getting things done, especially in midwinter. A pity the thyroid thing cropped up now. Try Ma Huang (a mild stimulant form of ephedra), B12, and light therapy. No guarantees, but I hear good things from others. My personal answer is to just live with the fact that things move slower at this time of year. Plus, it's easier for me to work with a more immediate deadline. Perhaps that's why I'm not a writer (ok, it could also be a total lack of talent). Stay warm! If your body is working to keep your internal temp up, it is taking energy away from your brain.