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.
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.
Ask the angels and the saints to intercede for you, just as you'd ask people who are alive. Stand face to face with them, in the belief that they are also standing face to face with you.
Prayers at home are an introduction, a preparation for prayers in Church. Thus he who is not accustomed to pray at home can seldom pray diligently in Church. Experience bears witness to this: anyone can observe it for himself.
Pray simply. Do not expect to find in your heart any remarkable gift of prayer. Consider yourself unworthy of it. Then you will find peace. Use the empty cold dryness of your prayer as food for your humility. Repeat constantly: I am not worthy; Lord, I am not worthy! But say it calmly; without agitation.
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.
Prayer... by its action it is the reconciliation of man with God, the mother and daughter of tears, a bridge for crossing temptations, a wall of protection from afflictions, a crushing of conflicts, boundless activity, the spring of virtues, the source of spiritual gifts, invisible progress, food of the soul, the enlightening of the mind, an axe for despair, a demonstration of hope, the release from sorrow.
Do you wish God to hear your prayer immediately, brother? When you lift your hands up to heaven, pray first of all, with your heart, for your enemies and God will grant you speedily whatever else you request.
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.
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.