The forgiver takes on the load. The forgiver extends a pardon to the offender and erases the consequences of his evil actions. But not every forgiveness is coupled with pardoning, often the consequences remain and have to be shared by the forgiver and the offender. The master accepts the pain and loss because he has compassion on the offender. That is pretty big compassion.
Forgiveness is a gift, a very big gift.
While the forgiver accepts the pain of the offender, he does not hang on to it but passes it on to God who takes it all. In the end, God repays his loss many times over. Forgiving with the mind only does not make sense. It seems like bad business, a real loss. Forgiving because you have to forgive just builds more resentment and anger.