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.
The one who prays ought never to halt his movement of sublime ascent toward God. For just as we should understand the ascent 'from strength to strength' as the progress in the practice of the virtues, 'from glory to glory' (2 Cor. 3:18) as the advance in the spiritual knowledge of contemplation, and the transfer from the letter of sacred writing to its spirit, so in the same way the one who is settled in the place of prayer should lift his mind from human matters and the attention of the soul to more divine realities.
How can one avoid distractions in prayer? If one abides in the presence of God. Indeed, when in the presence of one's judge and one's master, and speaking with him, one does not let one's eyes wander elsewhere. How much more should the one who approaches the Lord never turn away the eye of his heart, but fix it on Him who searches the reins and the heart.
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.
In this time of fasting and prayer, brethren, let us with all our hearts forgive anything or imaginary we have against anyone. May we all devote ourselves to love, and let us consider one another as an incentive to love and good works, speaking in defense of one another, having good thoughts and dispositions within us before God and men. In this way our fasting will be laudable and blameless, and our requests to God while we fast we will readily received. We shall rightly call upon Him as our Father by grace and we can boldly say to Him, 'Father, forgive us our debts, as we forgive our debtors' (Matt. 6:12),
Until we have acquired true prayer, we are like those who introduce children to walking. Make the effort to raise up, or rather, to enclose your mind within the words of your prayer; and if, like a child, it gets tired and falters, raise it up again. The mind, after all, is naturally unstable, but the God Who can do everything can also give it firm endurance. Persevere in this, therefore, and do not grow weary...
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.
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.
For while the body is bowed to the ground the mouth babbles idly, and the mind wanders here and there through the house, through the market place, how can such a person say he has prayed before the face of God? He prays before the face of the Lord who contains his soul in every direction, and withdraws it from all that is earthly, and, thrusting aside every human reflection, raises it up towards heaven.