I have never answered myself before...... :)
I regularly put in long days and know the toll they can take on your fibro. My saving grace is to find "interuptions" in my day to make me spur my mind and body.
For my mind I create time every few hours to check news and sports on the internet so that once done I can go back to my work with more concentration....I call it taking a break.
For my body I create moments that I get away from my desk and move around....light activity helps our Fibro.....