I use a scenario that actually happened to me to describe the fatigue. I was driving home from work one day and I was chewing a piece of gum. I got a wave of fatigue that was so crushing I couldn't even chew my gum . I had to spit it out because it was just too exhausting to chew and drive at the same time. When I tell that story, nobody has ever said 'oh, I know exactly how you felt'...yet .