Is that I have recurrent severe Piriformis syndrome, or posh Sciatica, if you will.
At the moment, sitting at my desk, I know that I am going to have an attack in the next few days.
It will be horribly painful, I will be on my own at home in the most miserable, crawling on the floor sense, and I won't be able to work. My boss will not understand that Sciatica is a crippling condition that can only be alleviated with rest (well, gentle movement but certainly not sitting at a desk for eight hours) and not just "back ache".
Thus will begin all sorts of aggro. I can't bloody wait.