Now that's easy. At the altar anyway. Remember the scene, you're standing at the altar, in front of the preacher, facing the most wonderful, most perfect person in the whole world and you vow before God and family and friends to forsake all others. Then you walk down the aisle as husband and wife and the journey begins. The journey to become one. The first thing we think of when we vow to forsake all others is other men/women. But what about the grey area? The thought life. And what about the other relationships of our life? Mothers, fathers, sisters, brothers, children, friends, co-workers, teachers, bosses? Did I vow to forsake them? Yes I did. How about sports, committees, hobbies, Girls Night Out, Guys Night Out? Did I vow to forsake those? Yes I did. People, places, things? Yes, these are all within the "forsake all others" definition. To what extent do I forsake? Whatever the relationship requires. Whatever is required to become one - one heart, one mind, one flesh. Whatever it takes.
Then the wonder is; we get it all back, every relationship in our life is doubled because our two lifes have blended into one and it's just twice - twice the joy, twice the sorrow. As a union we are more than we ever were as an individual.