It's easy to get hung up on someone else's mistakes. From the outside, you can see all the ways they could've done something differently. It's so obvious! Instead of wasting that energy on choices you can't control, examine your own.
Photo by Peter Lindberg.
While this attitude often manifests as a moral argument (glass houses and all that), business blog Entrepreneur argues that it's also a practical one. You can't control other people's choices, and you certainly can't control other people's pasts. Learning from others' mistakes is alright, but the longer you spend analysing how someone else could've done something better, the more you're just wasting time that could be put to more productive use.
Judgment not only can kill your career, it can dramatically decrease your ability to grow and move forward. Everyone has things they regret; that's a virtual certainty in our lives. Spending time learning from mistakes is productive, but spending time judging yourself or others for mistakes drains valuable energy better used elsewhere.
Of course, we all know why we really do it. It can feel cathartic to clearly lay out the reasons why someone else screwed up. "See, if only they'd retroactively listened to my advice, they wouldn't be in this mess." The problem is, even if you're right, you're still wasting time talking about instead of putting your energy towards something more productive.