They keep their friendships alive

A relationship that has consumed every other relationship in your life — where the partner has become the sole source of social connection, emotional support, and companionship — is not a fully healthy relationship, even if it feels close and warm. It is, structurally, a hostage situation: one person holding all the emotional eggs, which makes them both extraordinarily important and extraordinarily fragile. When that relationship faces difficulties, there is nowhere else to go. Mature partners protect each other's outside lives, not out of indifference, but because they understand that those lives are part of what made each person interesting. The friends, the pursuits, the relationships that existed before the couple existed — these are the roots that give the partnership stability. A person with full, active friendships brings more to a relationship than a person whose entire social world has collapsed into it. Keep the friendships. Protect the outside life. It's one of the things that keeps love from collapsing under its own weight.