It has been said that good judgement comes from experience, and experience comes from bad judgment. Unfortunately, one doesn't always learn good judgment from experience. From Russ Roberts' interview with Lawrence White over at EconTalk:While many learn only from experience, the implications of experience aren't obvious, especially on big issues. This is also a theme of Jim Manzi's new book, and is discussed here in an exchange with Connor Friedersdorf:
Lawrence White: I think the idea you referred to earlier of Friedman's, that people have to learn from experience that a certain program of control doesn't work, is true. And it was true in the Indian case. And so it's more about learning by doing. But I think somebody has to tell you what you need to learn from what you see. It's easy to learn the wrong lesson from experience.