They have the conversation before it becomes a problem

This is perhaps the hardest skill in long-term love, and the one that most distinguishes mature partnerships from those that run on avoidance. Saying the awkward thing while it's still a small thing — before it has grown, through weeks or months of silence, into resentment — requires a tolerance for momentary discomfort that most people don't have. It's easier to let it go, to hope it resolves itself, to decide it isn't worth the friction of raising it. It almost never resolves itself. The conversation you delay for six months is almost always harder, more entrenched, and more dangerous than the conversation you would have had on month one. Resentment compounds. What was once a small, addressable issue becomes a load-bearing grievance that has to be carefully managed rather than honestly resolved. Mature partners develop an instinct for catching the small thing while it's still small — and the willingness to have slightly uncomfortable conversations regularly so that large, destructive ones become less necessary.