I have often written about forgiveness on this blog, because I think the Christian injunction to forgive is widely and profoundly misunderstood - and not only by non-Christians.
The reason that Christians are called upon to forgive everybody and every-thing is that the alternative is to nurse resentment, which is bad for us - is indeed a sin, and one of the commonest (because officially encouraged) in this time-and-place.
There is no place for resentment in Heaven; so to enter Heaven we must be prepared to give-up all our resentments; and insofar as we harbour resentments during our mortal lives, then so much the worse for us.
Almost always, resentment harms ourselves, and does nothing whatsoever to whoever is resented.
For example, it is common to continue resenting people long after they have died - sometimes for many generations or centuries.
Resentment is therefore on the spectrum of that worst of sins: spite - whereby the desire to harm others is more powerful than even the desire to benefit oneself. Resentment is like that. It is a willingness to orientate one's life around negative desires for another person or people.
So, forgiveness is simply a recognition that resentment is a sin and does us harm; and repenting any resentments we feel.
This means that forgiveness has nothing to do with remitting just punishments, nor has it anything to do with forgetting - and failing to learn from - the harms that others have done to us.
Obviously, Christians need to learn from our experiences in life; and when other people have lied to us, stolen from us, assaulted us, tried to make us miserable or to destroy that which we most value - it would be idiotic to pretend this never happened!
As for other people asking us for forgiveness... well they shouldn't do it; and they would not do it unless they were deceitfully trying to manipulate others for their own benefit.
Anyone asking another human being for forgiveness is on the wrong side in the spiritual war. They should be asking God for forgiveness.
But even then, God Just Is merciful; so that forgiveness by God is a non-problem for anyone who has recognized their own sin and repented it.
Repeatedly begging God for the forgiveness promised by Jesus Christ to all who repent, seems likely to be a problem of not-really-repenting - and then asking to have the fact ignored.
If someone wants to repent, but somehow can't - then they should be repenting their failure to repent - and not psychologically-groveling to be forgiven despite not repenting!