[…] God has not commanded anything impossible for us, but only such things as we can do. Therefore, this can also be accomplished by everyone seeking the salvation of his soul. For if it were impossible it would be impossible for all lay people in general, then we should not find such a large number of persons who have achieved in the world this work of unceasing prayer duly.
One of the representatives of a whole line of such people is the father of St. Gregory [Palamas] of Salonica, that amazing Constantine who, although he was leading a court-life, was called the father and teacher of the emperor Andronicus [Palaeologus], and daily was occupied with state affairs, besides his household duties, having a large fortune and a troop of slaves, as well as a wife and children, nevertheless was constantly with God and so attached to unceasing spiritual prayer that he often forgot that the emperor or the courtiers were talking to him about imperial affairs and frequently asked about one and the same thing twice or even more.
This disturbed the other courtiers who, not knowing the cause of it, rebuked him for forgetting a matter so quickly and worrying the emperor by his repeated questions. But the emperor, knowing the cause of it, defended him and said: “Constantine has his own thoughts which sometimes prevent him from paying full attention to our affairs.” There was also a great multitude of similar persons who, living in the world, were wholly devoted to the prayer of the mind, as is testified in the historical records of them.
Therefore, my Christian brethren, with St. Chrysostom I implore you for the sake of the salvation of your souls, do not neglect the work of such a prayer. Imitate those of whom I have told you and follow them as far as possible. At first it may seem very difficult to you, but be assured, as from the face of Almighty God, that the very name of our Lord Jesus Christ, constantly invoked by you, will help you to overcome all difficulties and in the course of time you will get accustomed to this work and will taste how sweet the name of the Lord is. Then you will know from experience that this work is not only not impossible and not difficult, but on the contrary, both possible and easy.
That is why St. Paul, knowing better than we the great blessing that this prayer brings to us, commanded us to pray unceasingly [1 Thess. 5.17]. He would not have bound us by such an obligation if it had been extremely difficult and impossible, knowing beforehand that in that case, by not being able to perform it, we should inevitably prove disobedient to him and transgressors of his commandment, and should thereby deserve condemnation and punishment. And this could not have been the intention of the apostle.
Besides, take also into consideration the means of prayer, how it is possible to pray unceasingly, namely by praying with the mind. This we can always do if we want to. For even when we are sitting at some manual work, or what we walk, or take food, or drink, we can always pray with the mind and perform prayer of the mind, pleasing to God, true prayer.