Endings are difficult for me, especially when writing them. Sometimes I know what the ending is, or should look like, before I start writing the story. That does not make it any easier. As I approach the end of a novel I am working on, I'll want to rush to the finish line, or I'll worry about loose threads, or I'll wonder if the ending is satisfying enough.
There is reason to worry. A bad ending can ruin a book for a reader. An unsatisfying ending can leave them hanging. The goal is to bring a story full circle and to a satisfying conclusion. To leave the reader closing the book with a feeling of being swept away.
No pressure there.
A good ending feels like a natural conclusion to the story. Having someone or something new appear and save the day will not work. The characters have to drive the ending, with tools that were there earlier in the story. Author Raymond Chandler said, “The solution, once revealed, must seem to have been inevitable.”
A good ending shows growth in the character. Along with the external conflicts, a good story shows depth by taking its characters on an emotional path as well. This inner conflict is resolved by showing a change in the character, and gives the story heart.
It is satisfying to see a story come full circle. In some way, the end should resemble the beginning.
Make sure all subplots are resolved. Leaving loose ends is sloppy storytelling.
Don't philosophize to the reader. This is a common complaint about the ending of Dan Brown's novel, "The Lost Symbol" where the character spends too much time thinking about his experience while watching the sun rise. As James V. Smith Jr. explains in Writer's Digest, "Keep description to a minimum, but maximize action and conflict. You have placed all your charges. Now, light the fuse and run."