Reasons For Rejoicing

Μὴ χαίρε ὅταν εὖ ποιήσῃς τινὶ, ἀλλ' ὅταν ἀμνησικάκως ὑπομείνῃς τὴν παρεπομένην ἐναντιότητα. Ὂν γὰρ τρόπον αἰ νύκτες τὰς ἡμέρας, οὕτω αἱ κακίαι τὰς ἀρετὰς διαδέχονται. Ἅγιος Μάρκος ὁ Ἐρημίτης, Περὶ Τῶν Οἰομένων Ἐξ Ἔργων Δικαιοῦσθαι Source: Migne PG 65.949a

Do not rejoice when you do good to someone, but rather when you endure the assaults of adversity and are unmindful of injury. For in this way, night and day, vices are supplanted by virtues. Saint Mark The Ascetic, On Those Who Think Themselves Justified By Works