it is true, when I spend many hours playing poker there comes a time when you feel mental fatigue and also your body because you are sitting for many hours, what is recommended is in the 5 minute break to go for a walk and de-stress to recover energy, you should also plan the number of tournaments you are going to play that day, it will also depend on your state that day, not every day is the same, so you must have a plan to deal with each poker session in the right way.