This book introduces the reader to the results of the author's many years of research, reflections, doubts, and disappointments. It discusses how one can maintain health in our time, slow down the aging process, and preserve vitality and spirit. Nikolai Amosov, a prominent scientist and renowned surgeon, asserts that most diseases are caused not by nature, not by society, but by the person himself, his laziness, passion for pleasure, and habit of following stereotypes. In this book, you will find answers to questions: why do we get sick, what is health, and how can it be maintained for many years through a healthy lifestyle and physical activity. A surgeon, a world-class scientist, a thinker, a philosopher, and a talented writer, Academician Amosov always sought the truth along his own path, relying on his reason and optimism, the duty of a doctor and citizen, and a great love for people. A deep perspective on things and an accessible language of presentation—this book changes one’s worldview, in the best sense of the word!