I notice it almost always comes after some form of self-reckoning. It's rarely about the characters just bumping into each other years later and sparks flying. There's a weight to it. They have to carry the ghost of what went wrong the first time. In 'One Day', Emma and Dexter get that cyclical chance, and it's never clean—it's messy with career failures, bad timing, other partners. The author makes you feel the years between them, the parallel lives. That's the core for me: the second chance isn't a reset button; it's building a new bridge over the same river, knowing the currents are still there.
Some writers overdo the grovel, though. I've dropped books where one character spends 200 pages begging. It feels transactional, not earned. The best versions show change through action, not just apology. Quiet moments, like remembering how the other takes their coffee years later, or choosing a different argument path this time. That subtle shift in behavior is more convincing than any grand speech about being a changed person. It's the difference between telling and showing, and in second-chance love, showing is everything.