Acting, or pretending, can no doubt be very difficult. You have to walk around a wood somewhere in a leather caplet carrying a prop bow & arrow and somehow get people to believe that you're Robin Hood, not Gladiator in leather pants—that's a challenge. But listening to actors talk about how difficult acting is, the dark places that were oh-so-dark that they had to go to and somehow extract themselves from in time for lunch, etc? That's the most difficult challenge of all.
From MTV News:
Oscar-winning actor, singer, comedian and radio-show host Jamie Foxx found it hard to disconnect from his role as a homeless schizophrenic in the new movie "The Soloist." The part was so emotionally taxing that Foxx started therapy to help him cope with the role and keep himself separate from the character.
"It was something that I enjoyed, but it shredded me. I went to places that I never thought I would ever go," he said, according to Bossip. "I just remember being in my bathroom broke down, talking to my manager, like, 'I don't know if I'll be able to finish this.' "