I find I get mentally fatigued quickly. As a result I make sure to space out taxing things. For example studying for my exam. I started the second day of class. I studied a little bit every day or every other day. I was able to do well in my class because I didn't try and cram 8 hour study sessions 1 week before the exam. I also try to space out social events or things like that. If I know I am seeing friends for dinner on friday i'll make sure to have a nice easy day Thursday to make it easier on myself. If I cram to many things to close together i'm out of commission for a week or more so I had to learn the hard way