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.
Have great concern for these portals the eyes. Most robbers enter through these portals to overthrow the castle of the soul. Had the forefathers guarded their eyes, they would not have been exiled far from God and Paradise. 'The woman saw that the fruit of the tree was good...' (Gn 3:6).
When you intend to do something and see that your thought is perturbed, and if after invoking God's Name it remains perturbed even by a hair's breadth, know from this that the action you mean to commit is from the evil one and refrain from commiting it. For nothing done with perturbation is pleasing to God.
There is nothing more efficacious against the wiles of the devil, dearly beloved, than the kindness of forgiveness, and the bountifulness in charity, by means of which sin is either avoided or overcome.
Prayer is a branch (of a tree) of meekness, and freedom from anger. Prayer is an expression of joy and thankfulness. Prayer is a remedy against sorrow and depression.
If you love to enjoy true and complete delight from the Scriptures, seek to read them not merely with simple understanding, but with deeds and practical realities. Moreover, seek to read them not merely for the mere love of learning but also for the sake of ascetic endeavors & discipline, as St. Mark wrote: 'Read the words of Holy Scripture with an eye to practical applications and not merely to be puffed up by any fine thought that you may receive from it.' Another Father said: 'This is why the lover of knowledge must also be a lover of discipline. For knowledge alone does not give light to a lamp.'
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.
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.