It has been said many times already that real prayer is inner prayer, performed not only in words but also with mind and heart. Prayer of this kind captures the whole attention and keeps it within, in the heart. This is why to remain within is an inalienable feature of real prayer and its chief condition. The thought of God, as being present and listening to prayer, and the repulsion of every other thought is inseparable from remaining within in prayer. This is called sobriety or guarding of the heart.Therefore all the care of man striving to make progress in prayer must be pre-eminently directed and must in fact turn towards this end: that is, never to leave the heart, soberly protecting it from every thought, except the thought of God alone; and to do whatever one has to do with one’s attention never turning away from God, conscious of His presence, as though before His face. This is the highest doing in the work of prayer. Recital of prayer, practised in the manner shown above, is the way to this, and even to realising the need and necessity for it. It is the first to teach the mind to concentrate on the heart and to pay attention exclusively to God. Having learned the value of this concentration, it is natural for man, who practises prayer, to wish for it to become a permanent condition of his spirit; for then constant prayer would dwell in him; and desire naturally leads to efforts to satisfy it. All those who have felt this need have sought and seek this. All instructions of the holy fathers concerning sobriety and guarding of the heart lead in this direction and have no other source but achievements in this work.
If you feel this need, then you will ask: how to achieve this constant abiding within, before God’s face, with sober guarding of the heart? Recital of prayer opens the way and produces the rudiments, but does not reach the end itself, or does not bring it to the required force and perfection. Recital of prayers is complex. It contains and offers to the attention many subjects which, although holy, may remind one of the others, belonging to daily life or social life, and lead through these to worldly, irrelevant subjects, in accordance with the usual laws of association of thoughts and visualisations. And so it happens; the most assiduous recital of prayer can never be practised without the thought darting away and wandering outside. Since this disturbs the prayer and chagrined by it and does not wish to be delivered from this incapacity. Attention was drawn to this form the very earliest days of the life of spiritual endeavour. Then what method, following recital of prayer, was invented to cure it? The method was invented of saying short prayers, which would keep the thought of straying, nor of going outside. St. Cassian speaks of this, saying that in his time this practice was general in Egypt (Dicourses x.10). From the teachings of other fathers we see that it was used on Mount Sinai, in Palestine, In Syria, and in all other places throughout the Christian world. What other meaning have the invocation: ‘Lord have mercy!’ and other short prayers, which fill our divine services and our psalmody? Thus, here is my advice: choose for yourself a short prayer or several such prayers, and by repeating by themselves on your tongue, and keep your thought focused on one point only-remembrance of God.
Everyone is free to choose his own short prayers. Read the Psalms. There you can find in every Psalm inspiring appeals to your state and most appeal to you. Lean them by heart and repeat now one, now another, now a third. Intersperse your recital of prayers with these, and let them be on your tongue at all times, whatever you may be doing, from one set time of prayer to another. You may also formulate your own prayers, should they better express your need, on the model of the 24 short prayers of St. Chrysostom, which you have in your prayer book.
But do not have too many, lest you overburden your memory and lest your attention runs from one to the other, which will be totally contrary to the purpose for which they were designed- to keep attention collected. The 24 prayers of St. Chrysostom is the maximum; one can use less. To have more than one is good for variety and to enliven spiritual taste; but in using them one should not pass from one to another too quickly. Taking one which corresponds best to your spiritual need, appeal to God with it until your taste for it becomes blunted. You can replace all your psalmody, or part of it, by these short prayers; make it a rule to repeat them several times- ten, fifty and a hundred times, with lesser bows. But always keep one thing in mind- to hold your attention constantly directed towards God.
We will call this practice short prayerful sighings to God, continued at all moments of the day and of the night, when we are not sleeping.
Excerpt taken from the book- Unseen Warfare, by: Lorenzo Scupoli. Edited by: St. Nicodemus of the Holy Mountain, and revised by St. Theophan the Recluse.