I mean, he was head of a marketing agency, which in itself already implies a certain level of success (that many people can only aspire to). Seeing as how he was a consultant on the side too, I'm assuming that he's done okay for himself.

Perhaps he was judging himself too harshly. You're not going to win 100% of prospective clients anyway, so it's easy to interpret that as varied success, instead of just success that lets you keep going.