In the case of guarding one’s eyes specifically, praying to Hashem for help is absolutely critical. As the Ohr HaChaim asks: If someone has already fallen into tumah, how can he possibly control himself from sinning again? He answers by quoting the verse: Speak to the Children of Israel and tell them, “I am Hashem, your G-d. Do not perform the practice of the land of Egypt in which you have dwelled.” Explains the Ohr HaChaim, the Torah is addressing those who have “dwelled in Egypt” and became accustomed to seeing and thinking about tumah. They are told: “Tell them that I am Hashem your G-d” - that is, while human strength cannot possibly prevail, a Jew has within him “Hashem’s strength.” By tapping into it one can quash natural physical drives.
How does one reach that part of himself? As we have seen, one must merely daven for help. We will continue with several prayers specifically for preserving kedushah.
The Shelah HaKadosh writes:
I found the following manuscript from our Heavenly Master, HaRav Moshe Cordovero: A certain elder taught us that to rid oneself of an improper thought one should repeat several times the verse, “A permanent flame shall burn on the Altar; it should not be extinguished.” It was obvious to me that the elder was Eliyahu the Prophet, but the Master concealed the matter because of his great humility.
R’ Chaim Volozhiner writes:
Before one takes to the road, he should pray: “Master of the World! I am about to go to the Valley of Death (i.e., a place fraught with spiritual dan- gers), a hazardous place. Save me from the yetzer hara and from inadvertent and deliberate sins, and specifically from [a specific transgression].”
The Steipler writes:
A person should recite even one hundred times a day a short prayer to be saved from that sin and from improper thoughts. Even if he thinks that he has said the same prayer many times and it was not effective, he should not lose hope. Rest assured that ultimately the prayers will not return empty-handed, as time will tell.
R’ Elimelech of Lizhensk writes:
... And if he came across an improper sight, Heaven forbid, he should immediately recite the verse, “And you shall not stray after your mind and eyes” ... to avoid contaminating his mind.
R’ Shimshon Pincus writes:
In my mind, another strategy is to train oneself to pray with all his might at times like this. He should cry out from the depths of his heart for Hashem’s help. Even if he notices as he is crying out that these matters are still disturbing him, he should not be concerned but should continue crying out and praying for himself, saying, “Master of the Universe! See what is happening to me!” And he will see wondrous things over time.