In the past, I have stated that not all stories can end entirely happy. The reason behind this statement was my opinion on its overuse in many fantasy novels and mostly fairytale endings in general. While I believe that all endings in novels should not end happily ever after, I do believe that a good in-between is the way to go. An ending too happy is cliché because the reader does not get a truly satisfying story overall. While it can work sometimes, if the plot was focused on a more mature tone, it probably is not appropriate. Giving readers a bittersweet ending, with some of the characters being entirely happy while others are in complete misery, leaves more readers with a sense of union in the story. No matter which direction you go with the plot, you can still end your story on a different tone that will nine times out of ten still work. Bittersweet is the way to go for storytelling. Going for a depressing story instead like most of you probably interpreted me saying previously is not. Going for a completely dark ending for a story is just as bad as making the ending entirely happy. They are both cliché and the reader does not truly get rewarded in the end.
The last Hunger Games book Mockingjay took the dark ending route and because of this ended up angering a majority of fans. Although the Capital is taken down, almost the entire cast is left as former shells of themselves. For example, poor Katniss is cursed with terrible PDSD, seen as kind of a turncoat for killing newly elected President Coin, can never see her dead younger sister Primrose again, whom she fought the war for in the first place, and is left with almost no friends alive. Despite the content being realistic, the charm of the books in the first place was the feeling of hope and inner strength in even the most dire of situations. Characters still died, but optimism for a better future did not fade. The ending of the series replaces those feelings with an inappropriate depressing conclusion to Katniss overall, even if she was victorious in the war. The movie version of this ending fixed this issue with a much more optimistic tone, but the damage to the series still stands. If somehow the message of hope was mixed in with the realistic war tone, perhaps the story's ending would have been better. Even as not a fantasy novel, Mockingjay serves as a strong example as to why the ending of a story should not be too depressing.
Compare the ending of Mockingjay to another novel; the twelfth book of the Warriors series, Sunset. In that book, it ends with the main prophecy coming true of Brambleclaw taking down his evil younger brother in order to save his Clan leader. As Hawkfrost's, the younger brother of Brambleclaw, blood flows into the lake surrounding the territories of the four Clans, the story ends bittersweet. Brambleclaw stopped Hawkfrost from destroying the Clans by killing him in self-defense, but lost his sibling, whom he really loved in the process. Peace is restored but at a price. The reason this ending works over Mockingjay is because while bittersweet, it still rewards the reader for reading the six books leading up to this. From the start, a brotherly relationship was established between the two characters. At the same time though, there existed this feeling of tension as Hawkfrost from the corruptions of his father became more and more of a threat to Clan life. Constantly, Brambleclaw tried to restrain this change from occurring, but the state of Hawkfrost's mind due to his sense of justice being completely shaken turned out to be too much to control. It had to end the way it did. Otherwise, many cats would have died from a bloody reign by Hawkfrost. While bittersweet, the reader on the way to this ending was truly given an equally strong experience all the way through, something Mockingjay failed to provide.
The ends of a story must always justify the means. If your story establishes a strong moral of hope, make sure it ends on a strong note with the message of hope still applied to it. No one likes a dark ending for the heck of it. Either go bittersweet or establish the main plot element in whatever ending you choose for a more complete story. Writing is an art that should not be wasted, all because of the ending.