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.
Pray firstly to be purified of passions, secondly to be freed from ignorance and forgetfulness, and thirdly to be delivered from all temptation and forsaking.
Prayer is a great good if offered up from a thankful soul; if we are steadfast in it, so that whether we receive or do not receive what we pray for we at all times give thanks to God. For since He will sometimes grant what we ask and sometimes will not, in both cases it is to our gain... For oftentimes God will delay, not as denying our prayer, but in His wisdom seeking rather for our perseverance, and desiring to draw us nearer to Himself; as a loving father when asked by his son for something will often do; withholding consent, and not from the will to refuse, but rather to encourage him in steadfastness.
Oh, what great happiness and bliss, what exaltation it is to address oneself to the Eternal Father. Always, without fail, value this joy which has been accorded to you by God's infinite grace and do not forget it during your prayers; God, the angels and God's holy men listen to you.
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.
'If you do not feel like praying, you have to force yourself,' the Elder said. 'The Holy Fathers say that prayer with force is higher than prayer unforced. You do not want to, but force yourself. The Kingdom of Heaven is taken by force.'
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...
A great effort and much toil are needed in prayer before we can reach a state in which our mind is no longer troubled, and so attain the inward heaven of the heart where Christ dwells. As St. Paul says, 'Do you not realize that Christ dwells within you, unless you are worthless?' (cf. 2 Cor. 13:5).
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.
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 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.