An argument in favour of the statement is, as human beings, we do not possess the capability to completely wipe out memories from our minds, no matter how hard we may try. Also, memories involving pain and suffering are nearly always fresh in our minds, and it is the thoughts of this kind that we are told to forget, which is extremely difficult, and very rarely possible.
see more:to forgive is divine
In addition, some sins are so serious that to simply forgive and forget is not an option. Even Jesus himself enforced this point, when he told his disciples that one of them was going to betray him. He used the words it would have been better for this person had they never been born, which may sound a cruel thing to say, but what Jesus really meant was that it was going to be difficult to forget what Judas was about to do to him.
Another point strongly agreeing with the statement is, human beings can learn from their mistakes, and if sins and crimes were erased from our memories we would never learn. This is true, as we are not perfect, and we need to learn from our mistakes in order to make ourselves a better person.
On the other hand, it could be argued that forgetting is central to the forgiving process, and true forgiveness involves being able to move on and forget what was done in the past. If people keep bringing up what has been done in the past, and dwelling on it, then this suggests that forgiveness has not truly been granted, therefore, reconciliation does not occur.
Also, by refusing to forget what has been done, a person becomes consumed with regret, bitterness and anger, all of which are all destructive characteristics resulting in their lives becoming focused on mourning and revenge, and the motivation and ability to move on is lost. Constantly reminding someone of past feelings is un-Christian behaviour.
In conclusion, I believe that it is possible for a person to forgive, but I agree that it is not always possible to forget what they have done. Are we supposed to forget every time a person sins? Maybe we can forget the odd venial sin, but what about mortal sins, like somebody killing someone close to you? It is just not possible to forgive and forget about somebody who commits mass murder such as Myra Hindley, and we know that a victims mother, Anne West, can never forgive what Myra Hindley did to her daughter, and cannot bring herself to say the words, forgive us our sins, as we forgive those who trespass against us, in the Lords Prayer.
As Christians we all do our utmost to forgive and forget none of us are without sin, let those who have committed no sin cast the first stone.