I've eaten lunch at my desk for years and have none of the problems you mention as far as cleanliness. I also clean my desk a few times a week though and am not

I've eaten lunch at my desk for years and have none of the problems you mention as far as cleanliness. I also clean my desk a few times a week though and am not a complete dirtball. The mental fatigue thing is true though. However most of the time I just screw around on the internet during that time. I usually get up around 5-6am and have breakfast so I'm ready for lunch around 11. Everyone else seems to eat lunch closer to 1 which is just too long to wait for me.