After returning home to the west from Washington, D.C., he joined the motocross circuit and had moderate success, but he still could not make enough money to support his family. During 1962, Knievel broke his collarbone and shoulder in a motocross accident. The doctors said he could not race for at least six months. To help support his family, he switched careers and sold insurance for the Combined Insurance Company of America, working for W. Clement Stone. Stone suggested that Knievel read "Success Through a Positive Mental Attitude", a book that Stone wrote with Napoleon Hill. Knievel credited much of his later success to Stone and his book.