You always have to keep pushing to innovate. Dylan could have sung protest songs forever and probably made a lot of money, but he didn't. He had to move on, and when he did, by going electric in 1965, he alienated a lot of people. His 1966 Europe tour was his greatest…. The Beatles were the same way. They kept evolving, moving, refining their art. That's what I've always tried to do — keep moving. Otherwise, as Dylan says, if you are not busy being born, you're busy dying.

As quoted in Steve Jobs (2011) by Walter Isaacson, p. 570