How can one deal with distracting thoughts that disturb prayer?

First: Cling to the Lord. St. Isaac the Syrian says, “Sit before His face all your time, thinking of Him and recollecting Him in your heart, lest, seeing Him only after long you should not lack freedom of speech with Him on account of bashfulness. A high degree of freedom of speech is born from constant intercourse. Constant intercourse with men is of a bodily nature; that with God is psychic meditation and offerings in prayers … For the heart of those who seek the Lord rejoices. Seek the Lord, you sinners and be strengthened in hope in your thoughts. Seek His face by repentance at all times and you will be sanctified by the holiness of His face and you will be purified from your unrighteousness. Speed unto the Lord, you unrighteous, the Lord who forgives unrighteousness and effaces sins.”²⁹⁰

288 Hesychios the Priest, “On Watchfulness and Holiness,” in The Philokalia: The Complete Text, Volume I , trans., G. E. H. Palmer et al., eds., Nicodemus of the Holy Mountain, and Makarios of Corinth (Farrar, Straus and Giroux, 1979) 61: p. 172.

289 St. Mark the Ascetic, “On Those who Think that They are Made Righteous by Works” in The Philokalia: The Complete Text, Volume I , trans., G. E. H. Palmer et al., eds., Nicodemus of the Holy Mountain, and Makarios of Corinth (Farrar, Straus and Giroux, 1979) 147: p. 137.

290 St. Isaac of Nineveh, Mystic Treatises by Isaac of Nineveh , trans., A. J. Wensinck (Amsterdam: Koninklijke Akademie van Wetenschappen, 1923) 5 (73): p. 50 amended.

Second: Pray with the spirit of hope. St. Augustine says , “I seem to feel that for this reason he calls God gracious, because He bears with those failings of ours, and yet expects prayer from us, in order to make us perfect: and when we have given it to Him, He receives it gratefully, and listens to it, and does not remember those many prayers which we pour out unthinkingly, and accepts the one which we can scarcely find. For what man is there, my brethren, who, on being addressed by his friend, when he wishes to answer his address, sees his friend turn away from him and speak to another, who is there who would bear this? Or if you appeal to a judge, and set him up to hear you, and all at once, while you are speaking to him, pass from him, and begin to converse with your friend, who would endure this? Yet God endures the hearts of so many persons who pray and think of different things … What then? Must we despair of mankind, and say that every man is already condemned into whose prayers any wandering thoughts have crept and interrupted them? If we say this, my brethren, I know not what hope remains. Therefore because there is some hope before God, because His mercy is great, let us say unto Him, ‘For unto You, O Lord, have I lifted up my soul’ [Ps. 86:4]. And how have I lifted it up? As I could, as You gave me strength, as I could catch it when it fled away. … From infirmity I sink: heal me, and I shall stand: strengthen me, and I shall be strong. But until You do this, bear with me.”²⁹¹