Jamie Foxx digs deep to embody the true-life character of Nathaniel Anthony Ayers, a gifted musician who was sidelined by schizophrenia in 'The Soloist,' and he tells ET's Thea Andrews that the role was "therapeutic, but very scary."

"I had a childhood fear of losing my mind," says Jamie, who reveals that, "something bad happened to me in college. Somebody slipped something on me, and I flipped out."

Jamie says that for eleven months he thought he was "going to be crazy," and would play his music on the piano to soothe his mind. "That's what kept me who I am, so I really am [Ayers] in a sense. I really did go off to college, and something bad happened to me that messed with my mind, so all these different parallels made me understand what my character was really about."

The 'Ray' Oscar winner adds that in order to get into character he had to "go deep," and to maintain balance, "I would do jokes in between takes just so I could keep Jamie Foxx [present]."

In 'The Soloist,' in theaters April 24, Robert Downey Jr. stars as Steve Lopez, an L.A. Times journalist who meets Ayers, a homeless man who has a clear musical talent, despite working with only two strings on his violin. Lopez decides to write about Ayers, and soon discovers that he was once a Juilliard classical music prodigy whose promising career was sidelined by schizophrenia. Initially reluctant to take responsibility for Ayers, Lopez chooses to get involved with the troubled genius, leading to a life-changing friendship.

"Friendship, even when the chips are down -- that's what this story is about," says Jamie. "It's just two people getting to know each other in the most interesting circumstances."

Watch ET for more with Jamie, and watch the video to catch a list of his favorite things, from pizza to Green Eggs and Ham!