Remember the definition for sexual purity: you are sexually pure when no sexual gratification comes from anyone or anything but your wife. Our battle centers on our sexual gratification.
Let’s picture that gratification in another way. As a man, you need a certain amount of food and water to live. The amounts differ for each of us, based upon genetics, metabolism, and activity. It’s even possible to suspend these needs for a while, as when fasting or limiting your food intake to lose weight.
Similarly, you require a certain amount of sexual gratification. Your sex drive may be suspended by God with a gift of abstinence. And you can adjust the required volume of sexual gratification to some extent. By controlling the sexual images entering your eyes and mind, your system may become used to living on less, but in the end, you still have a certain volume of sexual gratification you need to fill.