I find it extremely difficult to keep control of my eyes.

Answer

As long as the presence of Allah Ta'ala, the Recording Angels and the closeness of Maut do not become realities, a person will in practical life conduct himself as if Allah Ta'ala and the Recording Angels do not exist. People abstain from sins in the public because their perception of the presence of people around them is vivid and real. They do not abstain because of fear for Allah Ta'ala. Despite believing that Allah Ta'ala is ever present, we commit the sins when others are not present. This is because our beliefs are dead. Our Aqeedah is lifeless.

To create life in our beliefs, Rasulullah (sallallahu alayhi wasallam) had prescribed remembrance of Maut and the Qabr in abundance. Every night you should devote a few minutes contemplating on Death and the Grave. Meditate on the pangs of death and the torments of the grave. If you do so regularly, every night, then Allah Ta'ala will create life in your beliefs. Genuine fear will then deter you from evil. Guarding the eyes and the mind will then become a simple issue.