Shippai wa seikō no moto (失敗は成功のもと): failure is the root of success. The Daijisen dictionary, as quoted by the magazine Serai, explains the proverb this way. After a failure, a person reflects on its cause and corrects the method and the weak points, so the failure leads to later success.
A related form, shippai wa seikō no haha, failure is the mother of success, has long been familiar. Serai notes that the simpler form with moto has become the common one.