Repentance as used in the Old Testament is a subject much loved by low church, moralistic, bible-thumping, protestant preachers. The Roman Catholic Inquisition......well let us not dwell on their methods of restoring sinners and backsliders to orthodoxy. Of course, bullying people to recant their heretical urges is not, and I suppose never was, the prerogative of the religious. How would party politics for example survive otherwise?
One of the essential outcomes of changing one's thinking, in essence admitting one can be wrong, is that one acquires a very different and broadening outlook on life. When one's mode of thinking has become addictive, a state which I fear afflicts most of us in one form or another, that change in thinking, which Jesus continually exhorted his listeners to adopt, can cut to the very heart of psychological denial. For me, that is the essential value of repentance. It requires experiencing regret and remorse, not difficult when that denial is displayed in the glow of enlightenment, because those twin experiences serve to aid the necessary change.
Once the habitual way of thinking has been broken, regret and remorse will have served their purpose and can be dispensed with. To persist in indulging in them does nothing for the individual except run the risk of slipping into other dysfunctions such as self pity. And this process of metanoia will still need to be continued, for one does not become a perfect as the result of a once and forever act.