Forgiveness always comes at a cost to the one granting the forgiveness. To not retaliate is to absorb the cost.
Timothy KellerWhile Christianity was able to agree with pagan writers that inordinate attachment to earthly goods can lead to unnecessary pain and grief, it also taught that the answer to this was not to love things less but to love God more than anything else. Only when our greatest love is God, a love that we cannot lose even in death, can we face all things with peace. Grief was not to be eliminated but seasoned and buoyed up with love and hope.
Timothy Keller