Strong Practice
Our pure original nature... is always functioning, all the time. If you attain this original nature, then it is possible to change your karma. But the only way to do this is through having a strong practice. This cannot be emphasized enough. You must perceive that karma is thinking: it is completely empty. It has no self-nature. You can perceive this yourself as your practice becomes stronger and clearer. In the meantime, simply don't make good or bad and this will soon become clear to you. At that point, what is your original face, your original substance? Nobody can give this to you, this is something you can attain only through the practice of meditation.