First, please keep in mind that you should not insist on their forgiving you because forgiving is that person’s choice.
Second, give the person time. That person may be angry and needs some time to process the anger.
Third, humbly and gently ask for forgiveness, knowing that the person may not be ready yet. Express regret as you ask for forgiveness. Try to make up for what you did, at least within reason.
The two most common triggers are seeing the person again if they are not in an ongoing relationship and dreams about the event and the person. These two commonly reignite anger. Another, if you are in a relationship with the person, is when the person reproduces the kinds of behavior that were hurtful in the first place. For example, suppose Person A calls you a disrespectful name. If Person A uses it again, it can trigger new anger in need of forgiving again.
Yes, I do see this happen. It is not an inevitable occurrence in most people, but it does happen with some. I think this occurs because of the psychological defense of displacement, which is transferring one’s angry feelings and behaviors, meant for a particular person, onto others as a way of trying to manage the anger. In other words, suppose Person A was hurt by his boss, Person B. It is too threatening for Person A to express that anger toward the boss. Yet, Person A still tries to release the pent-up anger and so it comes pouring out on others who will not threaten Person A once the anger is expressed.
An example of this is Person A displacing that anger onto his own children, who take that anger and learn to become angry. The children, then, once they grow into adulthood might end up displacing their anger onto their partner or their own children. This is one reason why forgiving is so important. It stops the unfair transmission of anger through the generations.
Even if God is asking you to forgive, you still have to cooperate with this and do your part. As an analogy, suppose your partner asks you for help in lifting some heavy bricks. You know the request and you know it is important. Yet, you still have the free will to help, when to help, or not to help. I think it is the same with your understanding of God. You are asked and yet it is your free will that helps you decide whether to forgive, when to forgive, and what actions in which to engage to bring about forgiveness. I would think of it as an interaction between God’s command or encouragement, grace for you to perform the act of forgiveness, and your will to be motivated to forgive and to engage in the actions of forgiveness.
Each person has to determine this right time. It will vary by how much experience the person has with the forgiveness process, who hurt the forgiver, how deeply the forgiver was hurt, and the support from others in forgiving.
Because forgiveness is a moral virtue and because people of faith and no faith can practice the virtues and can be motivated to grow in the virtues, then it follows that forgiveness need not be connected with a religion. Yet, some would say that forgiveness not only is your own actions toward an offender but also your cooperation with God’s grace to bring this about. From this perspective, religion as a dispensing of divine grace would be necessary for deep forgiveness.
Each person needs to assess his or her own level of hurt and own level of offending. If each was hurt, then each could practice forgiving. If each was offended, then each can ask for forgiveness. It is important to note where each person is on the forgiving process and on the seeking forgiveness process. They may differ on these and so patience is important. Finally, I recommend what I call “the three R’s of reconciliation:” remorse or inner sorry, repentance or sincerely apologizing, and recompense or making amends to the degree that is reasonably possible. Forgiving, seeking forgiveness, and the three R’s of reconciliation should aid in a true reconciliation process.