Could have, would, could
No one likes to regret. Still, we do it all the time, imagining what we could have done better in a given situation. It rarely feels good, but it's often useful.
Edith Piaf's world-famous chanson "No, je ne regrette rien" is a hymn against regret. James Bond's boss "M", played by Judi Dench, also finds the movement highly unprofessional. And in Friedrich Schiller's ballad "Die Bürgschaft", the poet makes it clear right at the beginning that repentance is only possible on the cross. These are just a few examples of the bad reputation repentance has. The latter is mainly due to the fact that this feeling typically comes over us after a failure.
One tried something, strived for a goal, but failed. One should have done this or that, but failed to do so – or simply chose the wrong thing. The repentant often suffers themselves, but sometimes others do too, such as the victims of an accident for which they are responsible. Pangs of conscience always require the insight that one made a mistake. Ideally, the person concerned even knows exactly what he should have done differently. Thinking about it is usually uncomfortable, but it helps to avoid similar incidents in the future…