As you pray and sing psalms to the Lord, watch out for the guile of the demons. Either they deceive us into saying one thing instead of another, snatching the soul’s attention and turning the verses of the psalms into blasphemies, so that we say things that we should not say; or, when we have started with a psalm, they cause us to skip to the end of it, distracting the intellect from what lies between; or else they make us return time and again to the same verse, through absentmindedness preventing us from going on to what comes next; or, when we are in the middle of a psalm, they suddenly blank out the intellect’s memory of the sequence of the verses, so that we cannot even remember what verse of the psalm it was that we were saying, and thus we repeat it once more….
We should persevere strongly, however, and continue the psalm more slowly, so that through contemplation we may reap the profit of prayer from the verses and become rich with the light of the Holy Spirit that fills the souls of those who pray.
~Nikitas Stithatos
Prayerful Life 