Imagine having just one relationship. The young man and woman marry and dedicate their hearts to each other. When they have sex together, it is a reflection of their true love for each other, and the love they have for the children that may be born from that union. In direct contrast, teenagers that engage in casual sex damage their own hearts and the hearts of their partners. Their ability to create a relationship of true love becomes damaged, as their heartistic antennae become rusty and dull.
True love is often completely absent.
Even when the partners feel strong emotion for each other, it simply doesn't compare to the closeness that can be attained when one devotes oneself to loving one person forever. Abstinence is the true love thing to do.