Between the two joys comes a ‘godly sorrow’ (2 Cor. 7:10) and active tears; ‘For in much wisdom is much knowledge; and he that increases knowledge increases sorrow’ (Eccles. 1:18).
The soul…is first summoned to the struggle by the initiatory joy and then rebuked and tested by the truth of the Holy Spirit, as regards both its past sins and the vain distractions in which it still indulges.
[...] The soul is tested by divine rebuke as in a furnace, and through fervent remembrance of God it actively experiences the joy exempt from fantasy.
When the soul is disturbed by anger, confused by drunkenness, or sunk in deep depression, the intellect cannot hold fast to the remembrance of God no matter how hard we try to force it.
Completely darkened by the violence of the passions, it loses totally the form of perception which is proper to it.
Thus our desire that our intellect should keep the remembrance of God cannot make any impression, because the recollective faculty of our mind has been hardened by the rawness of the passions.
But, on the other hand, when the soul has attained freedom from these passions, then, even though the intellect is momentarily deprived by forgetfulness of the object of its longing, it at once resumes its proper activity.
The soul now has grace itself to share its meditation and to repeat with it the words ‘Lord Jesus’, just as a mother teaches her child to repeat with her the word ‘father’, instead of prattling in his usual way, until she has formed in him the habit of calling for his father even in his sleep.
This is why the Apostle says: ‘Likewise the Spirit also helps our infirmities; for we do not know what to pray for as we should, but the Spirit Himself makes intercession for us with cries that cannot be uttered’ (Rom. 8:26).
Since we are but children as regards perfection in the virtue of prayer, we have need of the Spirit’s aid so that all our thoughts may be concentrated and gladdened by His inexpressible sweetness, and so that with all our being we may aspire to the remembrance and love of our God and Father.
For, as St Paul says, it is in the Spirit that we pray when we are taught by Him to cry without ceasing to God the Father, ‘Abba, Father’ (Rom. 8:15).
Diadochus of Photiké (c.400-before 486): On Spiritual Perfection chs 60-61, Text from G.E.H. Palmer, Philip Sherrard, and Kallistos Ware (trans. and eds.) The Philokalia: The Complete Text, vol. I (Faber & Faber, London & Boston: 1979).