In a mature narrative, the "happily ever after" isn't a destination, but a daily practice.

The beauty of a mature romantic storyline lies not in the initial spark, but in the strength of the "ties" that bind two people after the novelty has faded. These relationships are defined by a quiet, resilient intimacy—one earned through shared history, navigated crises, and the conscious choice to stay. 1. The Anatomy of Mature Ties

When writing these storylines, the conflict shifts from "will they or won't they" to "how will they endure."