What do you feel when you discover that your reasoning is flawed? when you find your recurring mistakes? when you find that you have been doing something wrong for quite a long time?

Many people feel bad. For example, here is a quote from a recent article on LessWrong:

By depicting the self as always flawed, and portraying the aspiring rationalist's job as seeking to find the flaws, the virtue of perfectionism is framed negatively, and is bound to result in negative reinforcement. Finding a flaw feels bad, and in many people that creates ugh fields around actually doing that search, as reported by participants at the Meetup.

But actually, when you find a serious flaw of yours, you should usually jump for joy. Here's why.