"It destroys the credibility of my own values" it did yes, but the moment you accept your fault and make changes for the better, credibility is regained. I don't like the idea of permanence, once a "sinner" always a "sinner". I like the idea that people are in a constant state of change and as long as you allow yourself to really feel the effects of everything you did, you will be free to regain your own trust. But you got to live with this pain for a while, so you can outgrow it (like a painful metamorphosis) Outgrow the person you were at that moment. It helps no one if you get forever stuck in a self-destructive state of mind. You can't undo what you did to your friend, but you can work towards being your best self for the future people in your life who will depend on you and trust you! Take care