Forgiving yourself is another way of giving yourself permission to get out of your own way. To see the truth for what it is, rather than hide behind it. If we take self-forgiveness moments, it changes our perspective, and therefore our approach to life. Our mood lifts, and we return to feeling happy and having that inner calm again.
My son has a rule of sevens to overcome sadness: seven hours, seven days and seven weeks. He allows himself to get sad or angry for a certain period of time. For him, it can be seven hours, seven days or seven weeks. When the time is up, he tells himself that he needs to move on and stops dwelling on situations that he can no longer change.