The ending of a novel should both satisfy and tease: the writer’s task is to tie up loose ends, although it can be effective (if a little irritating) to leave some of them unravelled. In this way, the story lives on in the reader’s mind as they try to answer open ended questions. Gone with the Wind is a classic example of this — I remember worrying away in my head about whether Scarlett would get Rhett back - if the reader knew for sure one way or the other they could let go more easily, which is not what you are after.

Another thing to consider is ending your story in such a way that it anticipates the future. This is not just for the purposes of writing a sequel — I’m not that cynical — but it can give your narrative ongoing momentum and in a strange way that enhances the reality of the world you and the reader have together created: it can coninue without you; somehow, it has an independent existence.