The evil spirit tries to scatter prayer as if it were a sand heap, tries to turn the words into dry sand, without coherency or moisture - that is to say, without fervor of heart. Thus prayer may become either a house built on sand or a house built on a rock. Those build on sand who pray without faith, absently, coldly: such prayer is scattered of itself, and does not bring any profit to him who prays; those build on a rock who, during the whole time of their prayer, have their eyes fixed upon God, and pray to Him as to a living person, conversing face to face with them.
Before the war begins, seek out your ally; before you fall ill, seek out your physician; and before grievous things come upon you, pray, and in the time of your tribulations you will find Him, and He will listen to you.
When you are praying alone, and your spirit is dejected, and you are wearied and oppressed by your loneliness, remember then, as always, that God the Trinity looks upon you with eyes brighter than the sun; also all the angels, your own Guardian Angel, and all the Saints of God. Truly they do; for they are all one in God, and where God is, there are they also. Where the sun is, thither also are directed all its rays. Try to understand what this means.
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.
When we return to prayer after a period of reading we find a rejuvenated and invigorated soul, stirred by the desire for God. The best form of prayer is one that implants the clearest idea of God in the soul and thus makes space for the presence of God within us. We become a temple of God when our continuous meditation on Him is not constantly interrupted by ordinary worries, and the spirit is not disturbed by unexpected emotions. Thus, in flight from all things, the spirit who loves God can approach God who drives out everything that leads us to evil, and holds steadfastly to everything that leads to virtue.
Prayer demands that the mind should be pure of all thought and should admit nothing not belonging to prayer, even if it were good in itself. As if inspired by God the mind should withdraw from all things and hold its converse with Him alone.
Prayer is truly a heavenly armor, and it alone can keep safe those who have dedicated themselves to God. Prayer is the common medicine for purifying ourselves from the passions, for hindering sin and curing our faults. Prayer is an inexhaustible treasure, an unruffled harbor, the foundation of serenity, the root and mother of myriads of blessings.
You describe how bitterly you regret the inefficacy of your prayers. Beware: to wish for consolation or revelation in prayer is a sure sign of pride. Pray humbly, in perfect simplicity, seeking salvation only through forgiveness, & having faith that God will extend to you His mercy - as He did to the publican.
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.
Fire makes iron impossible to touch, and likewise frequent prayer renders the intellect more forceful in its warfare with the enemy. That is why the demons strive with all their strength to make us slothful in attentiveness to prayer, for they know that prayer is the intellect's invincible weapon against them.