Here it is: You don't need to be sexually attracted to your partner to have great sex. Being admired by the person you love can be a gateway to arousal. Longitudinal research has consistently shown that sexual desire naturally fluctuates over the course of long-term relationships. What grounds you inside the relationships can also be the doorway used to access arousal that often leads to satisfying sex. The couples who continue to experience deeply satisfying sex over the long haul aren't necessarily the ones who never lost the butterflies.