I suggest that you begin to become a whole person. When they are gone, we feel empty. When you become whole, you are not dependent on others to feel wonderful. When you are whole and the other person is whole, entering into a relationship is a celebration between two whole people. This removes the need for the other person in a desperate way.
People go through many changes as time goes on.
A man is at combat with his evolutionary urge to mate with many females. Many males get very frustrated by this underlying desire. Many men leave someone they love, chasing this urge only to find that the emptiness they find is worse. My advice is to get spiritual. Make your top priority being connected to the indwelling Holy Spirit.