“But let us sinners, who feed upon crumbs from the tables of the rich, strive to acquire peace at least during prayer. This also requires a difficult and long-lasting struggle: completely cutting off the thoughts during prayer, renouncing the senses and the whole surrounding world, surrendering everything to the will of God, the unshakeable affirmation of the heart in faith, unquestioning faith in the power of God. With this affirmation of the heart, prayer becomes peaceful. “
(St. Arsenia of Ust-Medvedits, ‘Spiritual Instructions’ in pravoslavie.ru)