So what keeps us in love? That’s where the hormone oxytocin comes into play . Oxytocin is released by both men and women during physical contact and sex, especially during orgasm. This hormone deepens and strengthens the feelings of attachment to our partner. The more we release oxytocin, the more attached we feel. The endorphin system takes over, and we develop feelings of tranquility, stability, contentment, and safety within our relationships. These feelings can be maintained, keeping a couple together for many years, or they can erode over time.