Unfortunately, being able to forgive in a marriage can be very difficult, hence the very high divorce rate in America.
More often than not, when one person betrays another in ways large or small, the betrayal is not properly dealt with. The person betrayed doesn’t adequately expresse their dismay or the betrayer doesn’t sufficiently take responsibility for their actions. Instead, the transgression gets added to the bank of resentment that exists on both sides of the relationship, creating an imbalance between contempt and love. This can often lead to divorce.