Dealing with fatigue and reluctance to play is one of the advantages I believe cash games have over tournaments. If I'm playing cash, and I'm fatigued, I generally stop playing. Rarely have I looked back and found it was a good idea that I didn't stop playing while I was tired. And for reluctance to play, pretty much the same. If I'm reluctant to play, I don't.
For tournaments, it's obviously a different situation, since you pretty much can't just stop playing when you want to. I just try my best to begin a tournament well rested, well fed, and well hydrated. And if I find myself physically fatigued, I try to address any of those issues with food, or beverage. If mentally fatigued, I just do my best to stay focused and try to only concentrate on what I deem to be important. And on breaks, I just try to relax as much as I can, and if possible, try to enjoy some peace and quiet somewhere away from the game.
