The emotional peak begins at Alex’s (Sam Claflin) wedding to Bethany. Rosie (Lily Collins), having finally realized her feelings after discovering a hidden letter Alex wrote years prior, flies to the wedding not to stop it, but to speak her truth.
In a poignant, heartbreaking toast, Rosie tells Alex: "Choosing the person you want to share your life with is one of the most important decisions any of us makes. Because when it’s wrong, it makes your life grey. And sometimes, you don’t even notice until you wake up one morning and realize years have gone by."
The two don't reunite until they are 50 years old . The novel is a much more grueling exploration of a lifetime of missed chances, whereas the movie opts for a more traditional Hollywood timeframe to keep the romantic payoff sweet rather than bittersweet. Why the Ending Works