The bond between man and woman was designed to be strong. Some believe that the feminine and masculine duality is what keeps the universe in balance. In the past few decades our culture has eroded this bond. Now instead of attachment to each other, we have enmity instead.
Becoming physical with a person is supposed to reinforce the male/female bonding. Society has reduced sex to recreation. It is more powerful than that. This is why your first romance was so magical. That infatuation you felt was supposed to bond you to that person for the rest of your life.
The movie Captain Fantastic has a great scene that illustrates this point. In this scene, the boy experiences his first kiss. He becomes bonded with that girl to the point of vowing to cherish and protect her. This may seem absurd and creepy in this culture but for most of human history this was the ideal. This is the way it was supposed to be. Not the mess we have now.