Just as it is impossible for fire and water to pass through the same conduit, it is impossible for sin to enter into our heart if it does not first knock on the door of our heart by striking with a sinful image.
The great Law-giver Moses, rather the Holy Spirit, says to us, “Watch yourself, lest a hidden word in your heart becomes a sin” (Dt. 15:9).
“A hidden word” refers to the recollection of something evil that God despises. The holy Fathers call this an “assault,” which is launched by the devil in the heart. Observe, and you will see how the enemies of our salvation defeat us with fantasies, lies, and empty promises. Satan himself fell in the same way from the height of heaven like lightning because he fantasized about becoming equal to God.
Likewise, Satan separated Adam from God by
stirring his imagination and making him believe that he would become equal to God. This is how our false and cunning enemy usually tricks all
people who fall into sin.
The demons always lead us to sin via an empty and fake fantasy. With a fantasy related to the acquisition of money and greed they led
wretched Judas to betray the Lord and God of all. And with the false hope of a short-lived repose, honor, and glory, they made him hang himself and
led him to eternal death, rewarding him with the exact opposite of what they had presented to him with their fake fantasy; that is, with their assault
of evil thoughts.
First of all, there is an assault with an evil thought. Second, a dialogue takes place when our thoughts mingle with the demonic suggestions. Third, there is consent, when we contemplate the demonic
suggestions, and we decide to carry out evil. Fourth comes the physical action; that is, sin. If, therefore, we guard our mind carefully and push away the initial assault as soon as it appears (by resisting it and calling upon our Lord Jesus Christ), the next stages (dialogue, consent, and sin) remain inactive. The evil demon, because he is a bodiless spirit, cannot deceive souls unless he uses fantasies and thoughts.
St. Hysechios
http://agapienxristou.blogspot.ca/2013/01/sin-originates-in-mind.html
