The kingdom of God is always present for him who desires and wills it. When a man's disposition and way of life are like that of an angel, most assuredly this is the kingdom of God. For God indeed is said to rule as King when nothing worldly meddles in the governing of our souls and when in every respect we live not of this world. This manner of life we have within us, that is to say, we have it within us when we desire and will it. We do not need to wait a long time, or until our departure from this life; instead, faith and a God-pleasing life which accompanies faith are very near us.
The first duty of a Christian, of a disciple and follower of Jesus Christ, is to deny oneself. To deny oneself means to give up one's bad habits, to root out of the heart all that ties us to the world; not to cherish bad desires and thoughts; to quench and suppress bad thoughts; to avoid occasions of sin; not to do or desire anything from self-love but to do everything out of love for God. To deny oneself means, according to the Apostle Paul, to be dead to sin and the world, but alive to God.
He who reveres the Lord does what is commanded, and if he commits some sin or disobeys Him, endures whatever he has to suffer for this as being his desert.
The road into the Kingdom of Heaven was made by the Lord Jesus Christ, and He was the first one who traveled it. The Bible teaches that only he who follows Jesus can reach His Kingdom. But how can one follow Him? Hear what our Savior says about this: Whoever desires to come after Me, let him deny himself, and take up his cross, and follow Me (Mark 8:34). The words whoever desires mean that Christ does not compel anyone to follow Him. He has no need of the unwilling ones, but He desires that each person freely follow Him. Consequently, only those who willingly choose the Savior's path reach the Kingdom of Heaven.
The Lord commands all men to repent (Matt. 4:17), so that even the spiritual and those making progress should not neglect this injunction and fail to give attention to the smallest and most subtle errors.
But when the Holy Spirit dwells in the heart of a person, He shows him all his inner poverty and weakness, and the corruption of his heart and soul, and his separation from God; and with all his virtues and righteousness. He shows him his sins, his sloth and indifference regarding the salvation and good of people his self-seeking in his apparently most disinterested virtues, his coarse selfishness even where he does not suspect it. To be brief, the Holy Spirit shows him everything as it really is. Then a person begins to have true humility, begins to lose hope in his own powers and virtues, regards himself as the worst of men. And when a person humbles himself before Jesus Christ Who alone is Holy in the glory of God the Father, he begins to repent truly, and resolves never again to sin but to live more carefully. And if he really has some virtues, then he sees clearly that he practiced and practices them only with the help of God, and therefore he begins to put his trust only in God.
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.
Those who have sinned must not despair. Let that never be. For we are condemned not for the multitude of evils, but because we do not want to repent...
Four monks of Scetis, clothed in skins, came one day to see the great Pambo. Each one revealed the virtue of his neighbor. The first fasted a great deal; the second was poor; the third had acquired great charity; and they said of the fourth that he had lived for twenty-two years in obedience to an old man. Abba Pambo said to them, 'I tell you, the virtue of this last one is the greatest. Each of the others has obtained the virtue he wished to acquire; but the last one, restraining his own will, does the will of another. Now it is of such men that the martyrs are made, if they persevere to the end.'
When tested by some trial you should try to find out not why or through whom it came, but only how to endure it gratefully, without distress or rancor.