The more precious the relationship is, keep the appropriate distance.
Separately and together, the more precious the relationship is, the more independent and together they must be. If you keep eating delicious food, you get tired of it, and if you keep listening to good music, you get tired of it. It is not because there is a problem with the food or the music itself that you get bored. It is because the relationship between me and food, and me and music, which are too close, causes problems.
Separately and together, human relationships require appropriate psychological distance. Keeping the proper distance creates room in your mind. A good relationship lasts a long time when each other stands tall independently and stays together. Take a look at the giant trees in the forest. All trees are kept at a reasonable distance. Trees that are closely attached to each other cannot grow large. It's because each other gets in the way of growing big with each other.
The more important someone is, the secret to maintaining a good relationship is to maintain an appropriate distance.