I have forgiven my XAH for his infidelity, but it doesn't mean he has changed. In fact, he cheated on his wife (the mistress in our marriage), she cheated on him with his best friend, and to this day they have an unhappy, unhealthy marriage.
Forgiveness is for you...not for him. Forgiveness allows you to let go and move on. It may even say, "I love you", but it doesn't mean sacrificing yourself for something that is not good for you.