In short: there are limits. Morality plays a big role in a rich and full life, but it's not everything. And if your inner fire burns bright, no need to stoke it hotter. In any case, don't let yourself be fuelled by a sense of guilt or shame, but rather by enthusiasm and a lust for life. Be ambitious, not perfect. There comes a point when you're fine just the way you are.
Why am I writing this now, and not at the start of the book?
Simple: because most of us aren't there yet. Most people still have a long way to go and haven't come close to reaching the bounds of their moral ambition. And then the message is clear: stop wasting your talent and start making a difference.