There is one method which, if practiced with full attention, will seldom allow anything passionate to slip unnoticed into the heart. This is to examine our thoughts and feelings, so as to discover which they tend: towards pleasing God or towards pleasing ourselves.
Go, sell all that belongs to you and give it to the poor and taking up the cross, deny yourself; in this way you will be able to pray without distraction.
Rivalry over material possessions has made us forget the counsel of the Lord, who urged us to take no thought for earthly things, but to seek only the kingdom of heaven (cf. Matt. 6:33).
Unless humility and love, simplicity and goodness regulate our prayer, this prayer - or, rather, this pretence of prayer - cannot profit us at all. And this applies not only to prayer, but to every labor and hardship undertaken for the sake of virtue.
Prayer requires the inseparable presence and cooperation of the attention. With attention, prayer becomes the inalienable property of the person praying; in the absence of attention, it is extraneous to the person praying. With attention, it bears abundant fruit; without attention, it produces thorns and thistles. The fruit of prayer consists in illumination of mind and compunction of heart; in the quickening of the soul with the life of the Spirit. Thorns and thistles are a sign of deadness of soul and pharisaical self-esteem which springs from the hardening of a heart which is contented and elated by the quantity of the prayers and the time spent in reciting those prayers.
If you examine your life well, you will find many instances when God showed His unmistakable mercy to you. Trouble was brewing, but it passed you by for some reason. God delivered you. Acknowledge these and thank God, Who loves you.
The abstinent withdraws from gluttony, the uncovetous from covetousness, the silent from wordiness, the pure from attachment to sensory pleasures, the chaste from fornication, he who is content with what he has from love of money, the meek from agitation (anger), the humble from vanity, the obedient from objection, he who is honest with himself from hypocrisy; equally, he who prays withdraws from despair, the willing pauper from acquisitiveness, he who professes his faith from denying it, the martyr from idolatry – so you see that each virtue, performed even unto death, is nothing but withdrawal from sin; and withdrawal from sin is a natural action, not an action which could be rewarded by the kingdom.
A mind from which the thought of God has been carried away and which has thus become far removed from remembering Him, is also indifferent to sin with the outer senses. For such a mind can guide neither the hearing nor the tongue, since zest to work on itself has gone out of it.
A man is neither saved nor lost by the place he is in, but is saved or lost by his deeds. Neither a holy place nor a holy state is of use to him who does not fulfill the commandments of the Lord.
At this point the zealous man looks inward, and what do you think he finds there? Ceaseless wandering of thoughts, constant onslaughts from the passions, hardness and coldness of heart, obstinacy and disobedience, desire to do everything according to his own will. In a word, he finds everything within himself in a very bad state. And seeing this, his zeal is inflamed, and he now directs strenuous efforts to the development of his inner life, to controlling his thoughts and the dispositions of his heart. From directions on inner spiritual life he discovers the necessity of paying attention to oneself, of watching over the movements of the heart. In order not to admit to anything bad, it is necessary to preserve the remembrance of God. And so he sets to work to achieve this remembrance. But his thoughts can no more be arrested than the wind; his bad feelings and worthless impulses can no more be evaded than the stench of a corpse; his mind, like a wet and frozen bird, cannot rise to the remembrance of God. What is to be done? Be patient, they say, and go on working. Patience and labor are exercised, but all within remains the same. At last someone of experience is found who explains that all is inwardly in disorder because the forces within are divided: mind and heart each go their own way. Mind and heart must be united; then wandering of thoughts will cease, and you will gain a rudder to steer the ship of your soul, a lever by which to set in movement all your inner world. But how can one unite mind and heart? Acquire the habit of praying these words with the mind in the heart, 'Lord Jesus Christ, Son of God, have mercy upon me'. And this prayer, when you learn to perform it properly, or rather when it becomes grafted to the heart, will lead you to the end which you desire. It will unite your mind with your heart, it will cut off your wandering thoughts, and give you the power to govern the movements of your soul.
Since the enemy watches you constantly, waiting for an opportunity to sow evil in you, be doubly watchful over yourself, lest you fall in the nets spread for you. As soon as he shows you some fault in your neighbor, hasten to repel this thought, lest it take root in you and grow. Cast it out, so that no trace is left in you, and replace it by the thought of the good qualities you know your neighbor to possess, or of those people generally should have. If you still feel the impulse to pass judgment, add to this the truth that you are given no authority for this and that the moment you assume this authority you thereby make yourself worthy of judgment and condemnation, not before powerless men, but before God, the all-powerful Judge of all.
Set as a goal the kindling of the fire of the spirit, so that the spiritual fire will burn in your heart and, gathering up all your strength into one, will begin to build your inner man and finally burn up the tares of your sins and passions.
Do not be always wanting everything to turn out as you think it should, but rather as God pleases; then you will be undisturbed and thankful in your prayer.