I liken it to the saying, "Familiarity breeds contempt." When we skim the surface of some emotions, never digging deep or delving into their depths, we maintain a certain aloofness that allows us to be more objective and less involved. We seem to think clearer and our judgment is less impaired.
But, when we totally immerse ourselves in our passions, our deep desires, our longings . . . that's when we find contempt for ourselves, for others. To become familiar with someone or something is to lose compassion and charity. Our vision and judgment become clouded; we see "red."
I was taught while growing up that whatever passion we don't overcome will overcome us. It holds true for our deepest desires, some of which aren't noble. If something ignoble overcomes us and we give in to it, we end up hating ourselves or hating others.