Faith Above Understanding
We can try hard to guard our eyes and even make all sorts of barriers and penalties for ourselves, but if we aren't willing to truly give G-d our hearts, we will likely end up slipping again. What does it mean to give G-d our heart? It means that we need to be ready to accept Emunah upon ourselves without any understanding, Emunah that is beyond logic.
Using our "mind" and our "logic" alone is not enough in the battle with the yetzer hara. As we have seen so many times in the past, with all that we know and understand, we still keep slipping. This is because G-d wants us to give Him our hearts, not just our minds. He wants us to accept true Emunah upon ourselves, Emunah that is above reason.
Indeed, only when one's Emunah is stronger than his understanding will his understanding finally have a lasting value and be able to truly help him. As Chaza"l say: "Kol SheYiraso Kodemes LeChochmaso, Chachmaso Miskayemes - if his fear of heaven is greater than his wisdom, his wisdom will last."