"No Regrets." You've probably seen the slogan on a social media post, or as a poorly-spelled tattoo. But though we might view the statement as a motto for a well-lived life, adopting it as a rule can lead to the worst sort of life of all - one where we can't learn from our failures, we can't examine the outputs of our teams, and neither we nor our organizations can grow into the things we were meant to be. Let's examine regret together, because regret can be a powerful force for leaders! It can help you identify the most effective changes you or your organization can make, and allows you to find continuous improvement in your software - and in yourselves. But you need to learn the fine line between experiencing regret and wallowing in it, how to use upward counterfactuals to learn and downward counterfactuals to feel better about the present, and how to turn the development horrors you've lived through into a story that the people you work with will listen to. You can figure out how to learn from regret that isn't your own, too. Come learn how to master regret, and you'll even be able to learn from mistakes you haven't made yet!