I have had CFS/ME for at least 10-15 years. I used to hike and bike long distances and now can only manage walks (but at least walks still). Like many I am limited in many ways activity wise, but what I have not seen mentioned much is how badly my body shuts down if I go to bed just a bit later then usual. I have to be in bed by 8:30...latest 9:00. If I get caught out at an event and go to bed just a bit later, I crash. I can literally feel a switch turn off. It starts with me losing my voice, my breathing gets tight, and as it gets later I get shaky. I can feel a pulsing in my muscles. Worse of all is that if I miss my "window" I cannot fall asleep without a sleeping pill. The next day I am a mess, hoarse voice, tired lungs, exhausted, slightly fluish, shaky. I can't go out, travel, etc for fear of this happening. Also happens if my sleep is interrupted. Does this happen to others? Why would this happen?