When a person accepts anything Godly, then he rejoices in his heart, but when he has accepted anything devilish, then he becomes tormented.
Having accepted anything Godly, the heart of a Christian does not demand outside persuasion that it is from the Lord, but becomes convinced through the act itself that this acceptance is something heavenly, because he feels the spiritual fruits in himself: "love, joy, peace, longsuffering, gentleness, goodness, faith, meekness, temperance" (Gal. 5:22-23). But if the devil were to transform himself even into an angel of light (see 2 Cor. 11:14), or presented thoughts of the most worthy appearance, the heart still would feel some sort of doubts, trouble in its thoughts and disturbance of feelings.
The devil is like a lion, hiding in ambush (Ps. 9:29). He secretly sets out nets of unclean and unholy thoughts. So, it is necessary to break them off as soon as we notice them, by means of pious reflection and prayer.
During the singing of psalms, feats and great vigilance are demanded for our mind to be in conformity with our heart and lips; for otherwise stench is added to the incense in our prayers. For the Lord disdains a heart with unclean thoughts.
Let us continually, day and night, fall before the face of the goodness of God with tears, that He purify our hearts of any evil thought, so that we might worthily bring Him the gifts of our service. When we do not accept the evil thoughts put in us by the devil, we perform a good deed.
The unclean spirit has a strong influence only on the passionate; but those purified of passions he touches only indirectly and externally. A person in his youth cannot avoid being disturbed by physical thoughts. But he must pray to the Lord God, that the spark of depraved passions dies out at the very beginning. Then the flame within him will not become more intense.
