What are some of the signs that the constant pressure is wearing on Ender and his squad leaders?

After more battles, usually twice a day, Ender starts having nightmares about the fantasy game. Mazer wakes him one day for a battle while Ender is calling out in his sleep, to tell him that they have another battle. Ender is sleeping less and less. He and his squadron leaders begin to make more and more mistakes, and then one day, Petra becomes numb at the controls. She loses all but two of her fighters by the time Crazy Tom takes over, and they almost lose the battle. Petra is broken, no longer as reliable, and Ender relies on her less. The stress on Ender increases as well, and his nightmares get worse. One night he wakes up with a bloody hand from gnawing on it during his sleep. He tells Mazer that he thinks he is going insane.