Rabbainu revealed that there is an inner struggle taking place inside each person, that is why people in solitary confinement go crazy, because each person contains in him/herself elements and representation of all the 70 nations, aspects of all the different types of desires and lusts. When a person is amongst other people the different elements spread out and are concentrated on the people most suited to their aspect, thus one person will be possessed with the spirit of one nation, and another person a different nation. When a person is alone all the nations play themselves out in him and if he can't bring peace to them, he will not be able to have inner peace, and he will l"u go crazy.
R' Shmuel Horowitz, Saba Yisroel's good friend, was caught by the Russians when he was trying to return to Israel from Uman, they charged him of spying (Israel was under the Turks who were at war with Russia) and he was put in solitary confinement for more than 60 days, in inhumane conditions. R' Shmuel Horowitz writes that he never was zoche (merit) to have such amazing hisbodidus!