How do old couples keep their marriage for so long?

I've always wondered how older couples manage to keep their marriages strong for decades. In a world where relationships seem to fall apart so easily, what is their secret? Is it patience, compromise, or simply an unbreakable bond? Do they ever feel like giving up, and if so, what makes them stay? I want to understand what keeps love alive after so many years—through the struggles, the changes, and the ups and downs of life.