Defeat pessimism and increase your potential to live a healthy and happy life. In this work, psychiatrist Luis Rojas Marcos reviews the history of positive thinking, details the ingredients that distinguish an optimistic disposition from a pessimistic one, and explores the forces that shape our temperament (genetic baggage, character traits, and cultural imprints). He describes proven strategies to promote optimism and examines its impact on our relationship with others, our health and our career, as well as its most valuable quality: its power to help us face life's biggest adversities.