Franklin's obsessed with principles, which he thinks of as virtues: they're the guiding force of his life. For him, principles are more important than organized religion in terms of living one's life honorably and well, or of doing good. In his opinion, religion can keep people from really being honest in their virtuousness; principles help you work on doing good things for the sake of it. In The Autobiography of Benjamin Franklin, the hardest virtue to work on is humility (the opposite of pride), because even if you manage to be humble, that's something to be proud of. Thrift and frugality are easier to manage, but just as important: practicing them gives you time to concentrate on the things that matter, like improving your mind or working for the common good.
While Franklin spends a good chunk of the Autobiography telling us about his belief in virtue and the ways he works on it, we learn a great deal more about the kinds of virtues he practices from how he describes his actions.
Franklin's claims that he is committed to working on humility and diminishing his pride are, ultimately, undercut by his somewhat egotistical choice to write an autobiography in the first place.