I made a comment about Chronic Fatigue syndrome (CFS) on another thread about why all pioneers seem to get sick, but I thought that CFS might deserve a thread of it's own.
I remember one pioneer who said she had "Chronic Fatigue Syndrome." She read it in the Awake and she decided she had it. It was a syndrome that the doctors cannot prove or disprove, it is a syndrome that explains exhaustion when the other JW's say there is nothing wrong with you.
Gathering information not from Awake could be a real eye-opener to people like her. She probably really has CFS, but not because it is a feeling of exhaustion that the other JW's cannot say that she has. I imagine many pioneers and quite a few other JW's have CFS. (See http://en.wikipedia.org/wiki/Chronic_fatigue_syndrome)
Basically, CFS is mental and/or physical exhaustion that is unexplained. It is not at all like depression because it is primarily showing up as physical symptoms that are clearly more than just imagined. Because there is no medical test which is diagnostic of CFS, the disorder is a purely subjective condition which relies largely on patient history, and remains a diagnosis of exclusion. The patient has nothing else, so CFS is all that is left. Don't dismiss this- it is probably real. The mind is a tricky place.
CFS is persistent fatigue unrelated to exertion and not substantially relieved by rest. Some common symptoms are cognitive difficulties, severe mental and physical exhaustion. Pioneers especially, but all JW's, have to engage their cognitive skills all day if they actually speak to people about their beliefs, but also when they listen to and read WT beliefs at meetings and in the literature. They have to have their cognitive dissonance in high gear. (See http://en.wikipedia.org/wiki/Cognitive_dissonance) They are defending a ridiculous doctrine and dismissing all their personal independent thoughts that conflict with it all the time.
Also, I am sure that the imminence of the last seconds of the last days is wearing on them, wondering when it will finally arrive. That's got to add mental fatigue.