Even a pious person is not immune to spiritual sickness if he does not have a wise guide -- either a living person or a spiritual writer. This sickness is called prelest, or spiritual delusion, imagining oneself to be near to God and to the realm of the divine and supernatural. Even zealous ascetics in monasteries are sometimes subject to this delusion, but of course, laymen who are zealous in external struggles (podvigi) undergo it much more frequently. Surpassing their acquaintances in struggles of prayer and fasting, they imagine that they are seers of divine visions, or at least of dreams inspired by grace. In every event of their lives, they see special intentional directions from God or their guardian angel. And then they start imagining that they are God's elect, and often try to foretell the future. The Holy Fathers armed themselves against nothing so fiercely as against this sickness -- prelest.
Wherever we are and whatever our circumstances, the enemy always tries to prevent us from actively responding to the call. Pray for help. For help that you may never fail to respond. And beware lest, having received help and having done the right deed because of it, you should grow proud and acquire the habit of condemning others, in the secret chambers of your heart. Beware! For this would make all the fruits of your good works wither.
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.
Whether you pray with brethren or alone, try to pray not simply as a routine, but with conscious awareness of your prayer. Conscious awareness of prayer is concentration accompanied by reverence, compunction and distress of soul as it confesses its sin with inward sorrow.
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).
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.
Keeping the thought of God always present before you, this form of words for your devotions is ever to be put first: O God, make speed to save me; O Lord, make haste to help me. For this verse has, not undeservedly, been taken out of the whole of scripture for this purpose. It contains all the feelings that can come upon human nature; it is very rightly and properly suited for every situation and for every need that may come upon us. Indeed it contains a calling upon God against every danger, it has the humility of a good confession, the watchfulness of constant care and fear of God, it realizes the frailty of him who prays, exhibits confidence in an answer to the prayer, and trust in the Divine protection present and ever at hand. For he who ceases not to call upon his Protector is sure of His perpetual presence.
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...
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.
Do not pray that things may be according to your desires, for they are not always in keeping with the will of God. Better pray as you were taught, saying: ‘Thy will be done’ on me (Matt. vi 10). And ask thus about all things, for He always desires what is good and profitable for your soul, whereas you do not always seek it.