Main issues:
My first and most severe fatigue issues were the result of sleep apnoea. Whilst lifestyle effects are not all directly relevant to Web accessibility, I'll go through a few because these are issues that I would never have thought about, had I not had the personal experience, and I'm guessing that others would find the same.
Whilst technically able-bodied and with no sensory issues, fatigue can give rise to safety issues:
At one point, I could not work at all. Fatigue affects the ability to perform even simple tasks - start showering and have to start again as you can't remember where you'd got to. And as for using a computer...
And that should take us to our next slide.