Learning from your mistakes

The problem with learning 'only' from your own mistakes, as some people insist on doing, is that you may learn a lesson too late, and not have an opportunity to use that lesson again.

For example, the global market crash. Events of this magnitude occur once in a lifetime - some people probably don't ever experience anything of this sort. So if we refuse to learn the lessons from the Great Depression, etc and insist on burning our hands before we learn something from this one, the lesson is as good as useless.