[Simon] sighed. Other people could stand up and speak to an assembly, apparently, without that dreadful feeling of the pressure of personality; could say what they would as though they were speaking to only one person. He stepped aside and looked back. Ralph was coming along, holding his spear over his shoulder. Diffidently, Simon allowed his pace to slacken until he was walking side by side with Ralph and looking up at him through the coarse black hair that now fell to his eyes. Ralph glanced sideways, smiled constrainedly as though he had forgotten that Simon had made a fool of himself, then looked away again at nothing. For a moment or two Simon was happy to be accepted and then he ceased to think about himself. When he bashed into a tree Ralph looked sideways impatiently and Robert sniggered. Simon reeled and a white spot on his forehead turned red and trickled. Ralph dismissed Simon and returned to his personal hell. They would reach the castle some time; and the chief would have to go forward.
What is meant by "personal hell" in the quotation below?