Only those who forgive can be free - Hannah Arendt

"...he who acts never quite knows what he is doing, that he always becomes 'guilty' of consequences he never intended or even foresaw, that no matter how disastrous the consequences of his deed, he can never undo it...all this is reason enough to turn away with despair from the realm of human affairs and to hold in contempt the human capacity for freedom." - Hannah Arendt

But the possibility of forgiveness transforms the situation from tragedy to hope:

"Without being forgiven, released from the consequences of what we have done, our capacity to act would, as it were, be confined to one single deed from which we could never recover...forgiving, in other words, is the only reaction which does not merely re-act but acts anew and unexpectedly, unconditioned by the act which provoked it and therefore freeing from its consequences both the one who forgives and the one who is forgiven." - Hannah Arendt

So atonement and forgiveness are the supreme expressions of freedom, the freedom to act differently in the future than one did in the past.