Lust toward others outside marriage diminishes desire for your spouse — exclusivity of sexual attention is essential

If a man is consuming lust toward other women, it creates a mental beauty contest in which his spouse can always be outranked. The solution is to make your spouse the only contestant in that contest. When your spouse is the only person you look at sexually, they are automatically the most attractive person in the world to you. Cutting off every source of lust toward others will cause desire for your spouse to increase.