Oh, the fatigue can be awful. Today was an example for me. My sleep patterns are so screwed and sometimes I can sleep all night and sleep for hours during the day -- other times I don't get enough sleep at night and it's worse. Today I really should have ridden my bike but I was just so tired! I also was gone most of the day. But usually I would have been eager to work in a short ride at some point, anyway. Not today.