Answer: Just ONE person in a relationship can practice the Unification in that relationship AND benefit the relationship greatly. As you can imagine, if your partner spent some time thinking of you very fondly, you would feel their loving attitude the next time you meet. You would feel the shift whether your partner said anything about what had caused it. This clearly shows that while a relationship is made of two people, either partner alone, by raising their own orientation, can substantially improve in the relationship. Here's an experience to illustrate:
"The other day one of my co-workers was having a bad time. He was distracted, careless, and uptight all day. It was difficult to work with him, and it felt like I had to walk on eggshells so as not to make him react. Finally, at our company staff meeting at the end of the afternoon, I realized that I needed to make a bubble. My co-worker and I weren't having a one-on-one interaction at this meeting, but I began making a bubble around us and fairly soon felt softer within myself, and more connected to him. From within the bubble, I realized that my negative attitude towards this person had been making our relationship worse. The bubble changed my attitude to love and understanding. After the meeting was through, I felt close to this co-worker again and approached him. Even though he was still somewhat stressed from his challenging workday, our interaction was very warm and connected -- and the problems of the day were completely erased. Love truly saved the day."
As we align ourselves to a relationship in our minds and in our hearts, our attunement changes. Later on, when we meet the other person physically, we find that the relationship is upgraded. That's because we are now relating more from Self to Self, WITHIN Self, than from self to self, WITHOUT Self.* We enter into the spirit of relating from a higher place.
*Note: The word Self with a capital "S" refers to the higher Self -- the true and Godly Spirit of a human being. The word self with a small "s" refers to the human personality identified with the ego and directed by the lower mind.