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...
The most important thing in any good effort and the height of all activities is to persevere in prayer, by means of which we can always acquire through supplication the other virtues from God as well.
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.
To pray with self-constraint is in our power, whereas to pray with compunction depends upon God. We must pray with what prayer we can, and for our self-constraint God will give us compunction also in due time, when this is pleasing to Him.
Be fond of working with your hands, but still more of the memory of prayer; because the first does not always bring us the fruit of that occupation, while the second does so unceasingly. Do not stop praying until you have paid your due of prayer in full, and do not listen to the thought that it is time to sit down to work. Equally, when you sit at work, do not be too concerned in it, lest you agitate the heart by your haste and make it worthless for prayer.
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.
Do not attempt to assess the quality of your prayer. God alone can judge its value. To us, our own prayer must always appear so poor an effort, so inadequate an achievement, that the cry of the publican spontaneously rises from our lips.
He who prays with the lips, but neglects his soul and does not guard his heart, prays to the air and not to God; and he labors in vain, because God attends to the mind and fervor, and not to prolixity. One should pray with all one’s fervor, with one’s soul and mind & heart, with the fear of God, and with all one’s strength.