Hindsight is both a wonderful gift, but a terrible curse. Should have/Could have aren't going to help you to be kind to yourself or help you move forward positively. I bet you could stop anyone on the street and ask them if there were things that they could have or should have done differently in their lives and I bet every single one of them would reply yes... No point in using those to beat yourself with - life is tough enough. Be kind to you...