“The gates to brilliance are surrounded by a cloud of sweat and tears.” That is what Olympic dressage rider and coach Robert Dover’s mentor, the revered Swedish equestrian Colonel Bengt Ljungquist, told him. It is a lesson that stuck—only with great passion and determination can one achieve success, and just maybe, happiness, too. In a fascinating book that reads like a potent elixir, three parts memoir and one part inspirational self-improvement guide, readers are ushered through 16 “gates to brilliance”—keys that Dover discovered as he made his way through his own life,...