They say forgiveness is one of the most difficult things to give, even in married couples. It calls for humility, understanding, acceptance, and even pride. Very often, it's the pride that hinders people to forgive and forget the hurts from the past. Forgiveness has 2 parts - letting go and moving on. It's not enough to say that you have forgiven your partner, but then, deep inside you, you're still holding on and dwelling on the misgivings. Forgiveness could only be completed once you have learned to move on and forget the misgivings. In a marriage counseling session, you will learn why it's difficult to forgive.
Lack of understandingThe aggrieved spouse cannot understand the reason for hurting. It may be petty stuff like forgetting to pick up the clothes from the dry cleaner to the most serious ones, like say, an affair. There are many reasons why people get hurt and it can happen any time. The sad thing is if you cannot understand why your spouse has hurt your feelings because of lack of open communication.
“A great marriage is not when the 'perfect couple' comes together. It is when an imperfect couple learns to enjoy their differences.”
― Dave Meurer