Reasons For Rejoicing

Μὴ χαῖρε ὅταν εὖ ποίσῆς τινὶ, ἀλλ' ὅταν ἀμνησικάκως ὑπομείνῃς τὴν παρεπομένην ἐναντιότητα. Ὄν γὰρ τρόπον αἱ νύκτες τὰς ἡμέρας, οὕτω αἱ κακίαι τὰς ἀρετὰς διαδέχονται. Ἅγιος Μάρκος ὁ Ἐρημίτης, Περὶ Τῶν Οἰομένων Ἐξ Ἔργων Δικαιοῦσθαι Migne PG 65 949

Do not rejoice when you have done a good to another but rather when you have no memory of injuries received by an adversary, for so nights pass into days and vices into virtues. Saint Mark The Ascetic, On Those Who Think Themselves Justified By Works.