The demons cunningly withdraw for a time in the hope that we will cease to guard our heart, thinking we have now attained peace; then they suddenly attack our unhappy soul and seize it like a sparrow. Gaining possession of it, they drag it down mercilessly into all kinds of sin, worse than those which we have already committed and for which we have asked forgiveness. Let us stand, therefore, with fear of God and keep guard over our heart, practicing the virtues which check the wickedness of our enemies.
Our teacher Jesus Christ, out of pity for mankind and knowing the utter mercilessness of the demons, severely commands us: ‘Be ready at every hour, for you do not know when the thief will come; do not let him come and find you asleep’ (cf. Matt. 24:42-43). He also says: ‘Take heed, lest your hearts be overwhelmed with debauchery and drunkenness and the cares of this life, and the hour come upon you unawares’ (cf. Luke 21:34). Stand guard, then, over your heart and keep a watch on your senses; and if the remembrance of God dwells peaceably within you, you will catch the thieves when they try to deprive you of it. When a man has an exact knowledge about the nature of thoughts, he recognizes those which are about to enter and defile him, troubling the intellect with distractions and making it lazy. Those who recognize these evil thoughts for what they are remain undisturbed and continue in prayer to God.
When the intellect rescues the soul’s senses from the desires of the flesh and imbues them with dispassion, the passions shamelessly attack the soul, trying to hold its senses fast in sin; but if the intellect then continually calls upon God in secret, He, seeing all this, will send His help and destroy all the passions at once.