The counterexample of a mediocre person's success is that a mediocre person may remain mediocre if he does not firmly believe that he will succeed. For example, if Bill Gates has no self-confidence and goes out of the university campus to join the business community, how can he open a new era for Microsoft? If Jobs doesn't have the confidence to invent an apple that can change the world, how can he be proud of it? They may have been mediocre, but self-confidence made them successful!