I thought I'd start with this NLP presupposition because; this is the one that lets you off the hook. Not only lets you off, but everyone. As I have talked to people and reflected on my own life, it has become clear to me that we give ourselves and others a hard time for some bad decisions. So I always ask the question "if you were to go back to that decision and only had the information you had back then, would you make the same decision?" Surprisingly the answer is "no" most of the time.
This reminds me of a client that had decided to stay in a bad relationship even though it made her feel worthless. Her partner was cheating constantly and seemed to know that she would not leave. So her partner did little to hide the affairs even teased her with them now and again. She could see this for what is was and her refusal to leave made her feel worthless and destroyed her self-esteem, which in turn knocked her confidence. So we had a chat and when I asked the question would she make the same decision she said "no". So I asked her "If you only had the knowledge you had back then would you make the same decision?" Again the answer was "no". Ok So I asked "I would like to know what made you decide to stay?" She told me that at the time she believed it was better for her children so the decision could not be the best for her. Although her partner was not a good partner he was a good dad and she believed that keeping the family together was more important than her feelings. The next question was "If you had left and it did have a negative impact on your children would you feel better or worse than you do now?" After a short pause she replied that she would feel worse. The partner eventually left her, the children had at first been upset but they were old enough to realise that it was better for everyone that they had split. I pointed out the fact that at that time she could not have foreseen this, and asked at the time did she believe that the children could get any benefit from you leaving. Her reply was "no". So I spelled out the obvious, I explained that she had made the right decision at that time with all the information she had at that time. If she had made the decision to leave then, as she thought of it then, it would hurt her more to see her children suffer. She admitted that that was in fact the best decision that she could have made at that time but it was a bad decision. So the question is "would you make the same decision now?" "No" most people wouldn't, therefore you are not that person any more. You are feeling bad about making the best decision that you could. Now at this point some people realise that they are feeling bad for doing the best that they can and that's enough to feel good about making the best decisions, even if they didn't turn out that way. Others need some more work but ultimately it normally lessens the bad feeling if not eradicates it.
We have to make decisions even if we decide not to decide, which sometimes gives the decision to someone else. We also can only work with the information that we believe is true at any given moment. Most of the time there is always a better way and even if we know it for some reason it is not our better way at that moment. So "stop giving yourself and others a hard time" for the decisions that are made. Some decisions can be undone, some can't but you can decide something new even if it is to forgive.