The morbid details of the harm we do ourselves and the punishment awaiting us for sinning with our eyes may be useful to recall when quelling rising passions. Generally however, this kind of reflecting could prove too disheartening.
The Angel of Death has been described as a terrifying apparition with eyes all over, whose appearance delivers such a shock that the person’s soul departs (Avoda Zara 20b). What are those eyes, eyes and more eyes that affright the wretched victim so? Each one of them corresponds to a different forbidden sight that he allowed himself to view during his life, and it is the realization that he himself is the cause of all those eyes that shocks him to death.
But ill-gotten pleasures eventually have to be paid for. If only he stayed clear of such shameful viewing, the Angel of Death would not now be plastered with all those gruesome eyes to haunt his final moments, and his departure from this world would have been more peaceful.
Our sages call the yeitzer hora a first-class con-man. Artfully, he plies his trade around our eyes but woe to us if we buy his wares. When our time on earth is up and we lie helpless, he arrives in his true form, along with his cohorts, claiming the right to exact full punishment from the eyes that were so carelessly sold away into his hands.
Sometimes, those who sinned with their eyes are punished by the painful process of having their soul reincarnated. The Arizal says that when the soul of a sinner is reincarnated as a person, it is oblivious to any former existence. However, when it is sentenced to a term inside some member of the animal kingdom, it well remembers its former stature as a human being, the dignity and the pleasure it enjoyed, and its exalted Source - Oh, the agony of this tremendous comedown! (Sefer Chareidim, ch. 33).
Let us remember that one who transgresses the prohibition of gazing at what he shouldn’t will not be spared from punishment in gehenom - no matter how much Torah and good deeds he has to his credit.
The Steipler, ztz״l, however, points out the positive aspect of the above warnings. If there is heart-breaking punishment for our lack of discipline, then how fantastic must be the payoff every single time we exert ourselves to discipline our eyes and mind!