The Mirror of the Psalms

Καὶ μοι δοκεῖ τῷ ψάλλοντι γίνεσθαι τούτους ὥσπερ εἴσοπτρον, εἰς τὸ κατανοεῖν καὶ αὐτὸν ἐν αὐτοῖς καὶ τὰ τῆς ἐαυτοῦ ψυχῆς κινήματα, καὶ οὕτως αἰσθόμενον ἀπαγγέλλειν αὐτούς. Καὶ γὰρ καὶ ὁ ἀκούων τοῦ ἀναγινώσκοντος ὡς περὶ αὐτοῦ λεγομένην τὴν ᾠδὴν καταδέχεται· καὶ ἤ ἐλεγχόμενος ὑπὸ τοῦ συνειδότος κατανυγεὶς μετανοήσει, ἤ περὶ τῆς εἰς Θεὸν ἐλπίδος ἀκούων καὶ τῆς εἰς τοὺς πιστεύοντας γινομένης ἀντιλήψεως, ὡς εἰς αὐτὸν γενομένης τοιαύτης χάριτος ἀγαλλιᾶται, καὶ εὐχαριστεῖν ἄρχεται τῴ Θεῷ. Ὅτε γοῦν τὸν τρίτον ψάλλει τις εἰς τὰς ἰδίας θλίψεις συνορῶν, ὡς αὐτοῦ εἶναι νομίζει τὰ ἐν τῷ ψαλμῷ ῥὴματα· καὶ τότε τὸν ια' καὶ τὸν ιϲ' ὡς εἰς τὴν ἰδίαν πεποίθησιν καὶ προσευχήν ἐστιν ἀπαγγέλλων· καὶ τὸν μὲν ν' ψαλμὸν ὡς αὐτός ἐστι τὰ ἴδια τῆς μετανοίας ἑαυτοῦ λέγων ῥήματα, τὸν δὲ νγ', καὶ τὸν νε', καὶ τὸν νϲ, καὶ τὸν ρμα', ὅτε ψάλλει τισ, ούχ ὡς ἄλλου διωκομένου, ἀλλ' ὡς ὤν ὁ πάσχων συνδιατίθεται, καὶ ᾄδει τῷ Κυρίῳ ὡς ἰδίους τοὺς λόγους τούτους. Καὶ ὅλως οὕτως ἔκαστος ψαλμὸς παρὰ τοῦ Πνεύματος εἴρηταί τε καὶ συντέτακται, ὡς ἐν αὐτοῖς, καθὰ πρότερον εἴρηται, τὰ κινήματα τῆς ψυχῆς ἡμῶν κατανοεῐσθαι, καὶ πάντας αὐτοὺς ὡς περὶ ἡμῶν εἰρῆσθαι, καὶ εἶναι ἡμῶν αὐτοὺς ὡς ἰδίους λόγους, εἰς ἀνάμνησιν τῶν έν ἡμῖν κινημάτων καὶ διόρθωσιν τῆς ἡμων πολιτείας. Ἅγιος Ἀθανάσιος Ἀλεξανδρείας, προς Μαρκελλινον Εις Την Ἑρμηνειαν Των Ψαλμων

It seems to me that the Psalms are like a mirror in which one may contemplate oneself and the movements of one's own soul, and experiencing this one gives voice to it. And the one who hears what was read receives it as if they too had read the song, and having been impressed in like manner, sometimes it is repentance that is roused, or, attending to how God helps the hopeful one who trusts in Him, the listener too, as though the gracious help already were his own, rejoices and offers thanks. When it is the third Psalm, a man will ponder his own troubles, as if he thought the words in the psalms were such things; and then the eleventh and twelfth Psalms he will employ as the recital of his own prayer; and the fiftieth psalm he will take a the recital of the words of his own repentance; and when the fifty fourth psalm, the fifty sixth, the fifty seventh, and the one hundredth and forty two are sung, it is not as though someone else were being persecuted but that it were an account of his own suffering, and he sings to the Lord these verses as his own. And every other Psalm is spoken and arranged by the Spirit in the same way: in them the movements of our  souls are contemplated in them, and they speak of everything concerning us, and the words are as are own, for the recollection of the movement within us and as a correction of our condition. Saint Athanasius of Alexandria, To Marcellinus On the Interpretation of the Psalms