U.S. Olympian and former Technical Advisor for the U.S. Dressage Team Robert Dover works with Heather Mendiburu riding What Happen (œHappy), a 16-year-old Hanoverian Mare. Robert discusses the basic principles needed by the rider as well as the four major qualities a rider needs to own from half halt to half halt: rhythm, tempo, frame of the horse and length of stride. He also emphasizes the importance of visualization.