The worst kinds of mistakes to make are the ones that we don't bear the consequences for a long time, if ever. Some people make mistakes for others to pay them or at least clean up the mess. Am sure we can all relate one way or the other. The examples are quite numerous. For some people, so much time has past that they get away with denying ownership of such actions.
Of course it is good to forgot some things. Imagine a life that our every action or error has dire consequences and haunts us. That's certainly not what am talking about. Yet there is an obvious space for errors to completely be overshadowed by the happenings of current time. When that happens few actually think critically and recollect. We humans are actually quite good at forecasting and making predictions, but when it comes to reflecting and remembering the flaws of history we make obvious errors.
If anything we should turn more to the past when navigating the future because of the potential answers it weilds. It is one thing to speculate, but if there has actually been a precedent then turning for direction should be a no brainer. But as we are we tend to forget easily, which is why it isn't uncommon to see us collectively make the same mistakes. Then again, maybe we do know what history is telling us, but deliberately choose not to answer. It isn't exactly easy having to listen and learn from the past, but it sounds so much better than stumbling blindly into the future.