Endings sometimes come--just like that. The perfect scene or phrase pops smoothly (if something can be said to do that) into mind and there you are. The End. Finis. At other times the ending just won't end. Maybe you know what should happen but it would be disappointing or implausible. One way around the ending that won't is available for first person narratives and for the kind of authorial voice where there's an obvious storyteller. In either case the narrator admits straight up that s/he is having ending-trouble. Then s/he can say what ought to happen, but admit it didn't really. Or s/he can give an itemised rundown of what happened. In point form. That'll work.