Hindsight is an opportunity to realize your mistakes and also learn from them.
But with hindsight, you still may not learn from your mistakes except you take the time to look back on past events dispassionately. When you remove yourself from the poisonous web of disappointment and anger, emotions cease to interfer with the clarity of understanding. A better understanding should show you why you made those mistakes and how you could avoid them in future.
Also, with the benefit of hindsight, you should go back in your mind, and take a walk in the shores of someone who hurt you in the past. You may realize that you were not hurt intentionally. It might have been an error of judgment on the part of the one who hurt you. If it was a mistake, forgive and move on. If it wasn’t a mistake, still forgive and move on. Afterall, with the benefit of hindsight, you should realize that you are not really hurting anymore from ‘it’.