Evagrius Ponticus: Reading, vigils, and prayer

Reading, vigils and prayer - these are the things that lend stability to the wandering mind. Hunger, toil and solitude are the means of extinguishing the flames of desire. Turbid anger is calmed by the singing of Psalms, by patience and almsgiving. But all these practices are to be engaged in according to due measure and at the appropriate times. What is untimely done, or done without measure, endures but a short time. And what is short lived is more harmful than profitable.
Evagrius Ponticus, from The Praktikos, #15

St. John of New Valamo: The mind should not be idle.

Imagination and memory are one inner sense. Sometimes the memory of former events [i.e. sinful acts] hits us on the head like a hammer. At such a time concentrated prayer is needed, and patience too. Our memory must be filled by reading the Holy Gospel and the writings of the Holy Fathers; in other words, the mind should not be idle. Former events must be replaced by other thoughts, and gradually the former recollections will be crowded out and the melancholy will pass. In one heart two masters cannot live together.
+St. John (Alekseyev) of New Valamo, from Christ is in Our Midst: Letters from a Russian Monk, letter #26, dated Dec 20, 1947.