Athanasius Ad Marcellinum 11-13

11. … He who recites the Psalms is uttering the rest as his own words, and each sings them as if they were written concerning him, and he accepts them and recites them not as if another were speaking, nor as if speaking about someone else. But he handles them as if he is speaking about himself. And the things spoken are such that he lifts them up to God as himself acting and speaking them from himself. …

12. And it seems to me that these words become like a mirror to the person singing them, so that he might perceive himself and the emotions of his soul, and thus affected, he might recite them. For in fact he who hears the one reading received the song that is recited as being about him, and either, when he is convicted by his conscience, being pierced, he will repent, or hearing of the hope that resides in God, and of the succor available to believer – he exults and begins to give thanks to God. … And so, on the whole, each psalm is both spoken and composed by the Spirit so that in these same words, as was said earlier, the stirrings of our souls might be rasped, and all of them be said as concerning us, and the same issue from us as our own words, for a remembrance of the emotions in us, and a chastening of our life. …

13. … The Lord, being true Lord, not only made laws but offered himself as a model for those who wish to know the power of acting. It was indeed for this reason that he made this resound in the Psalms before his sojourn in our midst, so that just as he provided the model of the earthly and heavenly man in his own person, so also from the Psalms he who wants to do so can learn the emotions and dispositions of the souls, finding in them also the therapy and correction suited for each emotion.