QUESTION: I need to know if you can help me with a problem today. Advice from Miracles teachings about anger, specifically anger at oneself. Anger because a person did something they shouldn't have done or something they should have done, but didn't subsequently.They are now very angry with themselves. 
REPLY: Since anger is a manipulation tool, I think we can rule it out as the emotion involved. It sounds like frustration might be a better description. And frustration is a manufactured emotion. 
Sometimes the rules we set up for situations don't really fit our reality, so we get frustrated----but most times, it's not at ourselves for falling short, though we pretend it is. Usually, it's at the unreasonable expectations of ourselves or others. A simple case of conflicting beliefs.
Sometimes, I get frustrated when I can't do all the things I did when I was 19. Somehow, my expectation is that I should. Something's got to give since I resist adjusting my expectations, so I produce frustration instead, when --clearly-- my expectations are not aligned with my beliefs about reality, and that's the real problem. 
My belief that I should be able to do all the things a 19-year-old can do conflicts with a basic belief that someone older can't.  So, the only reasonable course is to adjust my expectations or change my beliefs---and both are hard to do. Frustration is easier, and it get's me off the hook. So, I manufacture that instead of solving the obvious problem.