Fatigue for me often means I have the feeling of having been in a swimming pool for hours and it is that "heavy body feeling" you get when you climb out of the water. Just moving wears me out. Fatigue also necessitates breaking down tasks into bits and pieces and taking frequent breaks. And sometimes I think my brain gets fatigued just fighting the stress and physical fatigue 24/7.

And yes, the worst part is the unpredictability! You can be up for an activity right up to the point of starting it, and 'wham!' the energy and ability is gone! Gr-r-r-r! I hate that!