I think so too. If the next time you can change something you would have done, such that less people suffer or die, then it seems like you should go ahead and do that. In the end this is the simple rule.

Sometimes you just didn't have the complete picture and you might have been acting ideally given the limited information you had; that is, if you changed your behavior, it might change for the worst in other situations. It's not about self-punishing, it's about learning!