Mary was prepared or at least willing to forgive Ted of potential mistakes because that was the Christ-Like thing to do for a good Christian woman that she wanted to be. She thought about how she could do this if he were unfaithful, or if he made some other big mistake. After much thought, she decided she could. She would forgive him of unfaithfulness or some other equally serious mistake. However, as we look in on Mary's life, we notice something very contradictory.
Mary is a stickler on manners and social graces. Ted falls short here and Mary needs to constantly remind him of his shortcomings in this area, ted also purchased a boat with money that would have been better spent on carpet, and he has never heard the last on it. Ted also accepted a job that later paid much less than expected and Mary constantly reminds him of this mistake. She also cannot tolerate his failures in many other little things. Well, this listing could go on, but as you can clearly see that for Mary it is harder to be forgiving of little daily mistakes than the big ones. Well, we may not have to forgive any real big mistakes but the little ones are sure to come.
Having a long term memory is usually seen as an advantage in human relationships. We want to intellectually be aware of past tendencies in the other person so that negative experiences can be avoided or prevented in the future. But, if people are to change for the better they need to be believed and accepted in their changed form. Retaining the past is a definite detriment to this. Excellent and scholarly books have been written on the psychological benefits of forgiveness. It seems very clear from the studies that better relationships emerge when there is forgiving of errors.
Change is much more possible and other elements helpful to positive relationships such as love and trust emerge when forgiveness, rather than a lasting memory is present.