How should one best deal with being unforgiven by another? What to do when a sin is committed, forgiveness is begged, but a sharp grudge remains against?

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Since it is incomparably the greatest dignity to be introduced into the company of angels, nay, to be made the associates of Christ, he who estimates this favor of God aright, will regard all other things as worthless. Then neither poverty, nor contempt, nor nakedness, nor famine nor thirst, will make his mind so anxious, but that he will sustain himself with this consolation. "Since the Lord has conferred on me the principal thing, it behooves me patiently to bear the loss of other things, which are inferior."--John Calvin