Fatigue (for me) is when someone has let the air out of my tyres, and brain fog rolls in so I can't move fast, everything about me (including my brain) is in slow motion - while the rest of the world is at normal speed - and nothing computes, except a feeling of hopelessness and helplessness when it's really bad.

I almost feel disconnected from reality. I stumble through physical movements like a drunk, trying to communicate using words that I can't seem to find, and thought processes that I can no longer put into any semblance of order, with little retention of information.

And it can come on just like flicking a switch - no warning - just bam!