I'm not sure how useful this kind of thinking would be in actual practice. People regret the things they didn't do more than those they did? No kidding. But it's not always possible to do everything, and it seems like people who don't regret anything are either kidding themselves or have just learned to tune out regret. I remember reading that they key to a study done showing levels of happiness was mostly about managing expectations. Even hackers and captains of industry eventually have to learn this lesson.