The inscription on the Oracle of Delphi says: 'Nothing in excess.' C.S. Lewis described temperance as going to the 'right length but no further.' Easy to say, hard to practice - and if it was tough in 300 BC, or in the 1940s, it feels all but impossible today. Yet it's the most empowering and important virtue any of us can learn. Without self-discipline, all our plans fall apart. Here, Ryan Holiday shows how to cultivate willpower, moderation and self-control in our lives. From Aristotle and Marcus Aurelius, to Toni Morrison and Queen Elizabeth II, he illuminates the great exemplars of its practice and what we can learn from them.