Willpower and self-discipline lead to success. It is perhaps the most famous experiment in the history of psychology: a child is presented with a marshmallow and has a choice - eat it immediately or wait to receive two later? Will they hesitate or go for it? And what does this decision mean for their future life? Walter Mischel, a world-renowned psychologist and inventor of the marshmallow test, demonstrates in his book how self-discipline shapes our personality - and how it helps us, in moderation, to master our lives.