Great question, Oxygen. I would get very tired, too (although not the headaches). What stopped this was exercising!! I would run first thing in the AM, even if I had to wake up early. Then, whenever I got the chance I would exercise some more. Even if it was just a walk along the river, or taking my son to the park. Other people on the Master-Cleanse have had this response to exercise as well. Good luck! And get moving! Get those toxins worked out.