How do I stop blaming myself for not being more successful

Take time to detach yourself from the need to measure being successful and judging yourself.  Its likely your definition of success hasn’t been fully made conscious and as a result is some general idea you will never live up to.

If you have goals work toward them. If you struggle adjust. As long as your learning and engaged in life your successful. This ‘blaming’ will only help you if your doing it to learn how you might do/be better other wise its just a excuse to keep you stuck