Endings are hard. They're as hard as beginnings, and sometimes harder. With a beginning you have a blank slate, with nothing but the reader's expectations. By the end you have an entire story to deal with on top of those expectations. You can't let the reader down by just slapping an ending on there or letting them decide.
Sometimes you have the ending planned out--the entire story was building up to this, this one moment. Sometimes you figure out the ending as you write, and the story leads you on to a place you didn't expect but know in your heart is right. And sometimes--sometimes you have to choose.
I'm admittedly leery of using Blue Star as an example for this post, because it's a mystery, a thriller, and the ending is, well, spoilery. So I'm not going to say details, just vague stuff.
Star has a Punnett Square ending choice. (For those of you who never took biology, this is what I mean.) I had different variables, different things that could happen to the setting, the main characters, so on and so forth. There were two massive variables that would affect the entire story. I'll call them X and Y, for brevity's sake.
So now I have this.
X DOES NOT HAPPEN
X AND Y HAPPEN
Y HAPPENS, X DOES NOT
Y DOES NOT HAPPEN
X HAPPENS, X DOES NOT
X AND Y DO NOT HAPPEN
So which ending do I give the story? What message do I want to send? Things will be very different depending on which one I choose. Which ending does the story deserve?
It can be a tough choice, and an agonizing one. I managed to get input, and talk it over with some of my betas, getting input on which endings would sour the reader or make them feel like they got shortchanged. In the end, though, it's my story. No one else can write it for me, and I have to take these opinions and my own and pick the ending I feel is best. Don't feel you have to suddenly make the hero and heroine get together. If the story ends with the bad guy winning, then the bad guy wins, and maybe you can write a sequel. Haha. Sometimes you can give your readers the happy ending.
But sometimes, they don't live happily ever after.