We have a non-Jew on our Chizuk list for a long time already who has totally broken free from the addiction to masturbation and porn for over two years already. When we asked him what was the secret of his determination, this was his reply:
I have no secret other than the memory of the ordeal of suffering - both physical and mental, that I went through as a consequence of masturbation. To be quite frank, I'd rather die than experience that living death again. Even the shame would be enough to kill me. I know from personal experience that what the Rabbis say is true regarding the absolute need for sexual self-control. It truly is the foundation of manhood- and everything associated with being a more complete human being.
I also found this passage from a book that I intend to read to be rather inspiring. From "The Jugurthine War" by Gaius Crispus Sallust:
"It is the unfounded complaint of mankind that they are naturally weak and short-lived, and that it is chance, not merit, that rules their destiny. So far is this from the truth.... The mind is the guide and commander of life in mortal men. Where it has become the slave of low passions and has succumbed to sloth and bodily pleasures, a short submission to the fatal influence of lust suffices to fritter away strength, opportunities, and intellect, in idleness, and then the weakness of our nature receives the blame, and the doers charge circumstances with the defect that lies in themselves... The mind is pure and eternal; itself ungoverned, as the guide of man, it moves and governs all things. Hence we may be the more astonished at the degradation of those who surrender themselves to bodily pleasures, and spend their life in luxury and sloth, while they allow the intellect, the best and noblest factor in man's nature, to become inert from indolence and neglect..."