Everyone carries some festering situation or memory that requires energy to keep the issue going.The grevience may well be founded in reality and the righteousness of your position may be valid but what is the value of retaining it? The person or situation is part of the past and keeping it alive may prevent you from experiencing more positive pursuits .Putting a time limit on the situation may free you up to move the energy into more productive goals.It is not merely the need to forget because that may not be possible. But it is possible to rationally remind yourself that the statue of limitations will allow you to not be captive to the past.