The only problem for-seen with this antidote for a narcissist is that they are very good actors. They could role play their revelation while demonstrating to you how it will take time for them to relearn bad behavior. This plays on the sympathy and patience of a real genuine and kind person who has suffered, tolerated and put up with narcissistic abuse. The merciful person thus let’s their guard down only to play into the evil hands of the narcissist over and over again. While the narcissist is claiming it is a learning process for them, the true victim is continuing to suffer at the hands of manipulation that is engulfed in deceit.
I have known narcissists who have even gone to counseling over and over while berating the wife as being the culprit of their unhappiness. Many counselors are not plugged into narcissistic abuse and the dynamics of it's evil nature. If a narcissist wants change due to understanding their formidable years of childhood abuse or otherwise they will agree to medical and/or psychological intervention while truly changing their behavior. If you don't see humility, genuine repentance and transformation...the narcissist is just playing another game.