This sounds cliche but something that shouldn't be joked with. Many people spend their entire lives carrying the problems of their past. They refuse to forgive themselves. Some tell themselves, it's my fault, even when it clearly wasn't. They think that if they tell themselves this enough they would believe it and it would help them avoid such mistakes in the past. Truth is this works, but you damage yourself when you blame yourself every time for your mistakes little or large. You end up having nightmares because you have refused to forgive yourself and let go of the past.
Fun fact, do you know that if you find it difficult to forgive yourself, you will also find it difficult to forgive the mistakes of others. It would even be worse when others wronged you deliberately. You won't ever forget their wrongs and soon you will seek revenge. This is the tale of so many who are waiting on trial or rotting in prison. Well, some have avoided prison but are locked in the prison of their minds.
You will never experience true freedom if you don't learn how to forgive yourself. I want you to know and remember everyday that you are a human being. Human beings are bound to make mistakes. When you remind yourself of this, you are more aware of yourself, love yourself and stay sane. When you have total mental wellbeing, you end up making less mistakes. You improve yourself and you feel more confident. You bear no grudges with people and live a life worthy of emulation.
This is a life worth living. A truly happy life. Please dear, forgive yourself and forget your past mistakes.