“Flow” refers to a state of complete focus, peace of mind and instinctive action. This elusive state of mind is the subject of author Steven Kotler’s new book, “The Rise of Superman: Decoding the Science of Ultimate Human Performance.” The author spent over a decade studying extreme athletes to understand how flow has propelled them to physical feats that were once thought impossible. Kotler argues that once we understand how flow works, we can use it to improve performance in all aspects of life.