The Losers Remember
In Stephen King's novel, after defeating It, the Losers all begin to gradually lose their memories of what happened. Mike observes that this time, it's happening to him too, even though he's stayed in Derry, and muses that this must mean that It is truly dead this time. He attempts to write about their experiences in his journal, but in time, that, too, begins to fade, and he gives up. He is sad that he won't remember his friends but figures that this may mean that they'll all get their happy endings now, without the grief and trauma that would accompany their memories of what they shared.
It Chapter Two takes the complete opposite tactic, showing that the Losers each still remember everything, even long after leaving Derry. The film shows that they're staying in touch with one another, moving on, and that each of them seem happier and more content than they did at the beginning of the film.