"Ideas, in a sense, are overrated. Of course, you need good ones, but at this point in our supersaturated culture, precious few are so novel that nobody else has ever thought of them before. It's really about where you take the idea, and how committed you are to solving the endless problems that come up in the execution." - Hugo Lindgren, "Be Wrong as Fast as You Can", New York Times Magazine, Jan. 6, 2013 (italics mine)
Writers get asked where they get their ideas all the time. I confess I find this rather frustrating, because it implies that once you've got an idea for a story, the hard part's over.
As Mr. Lindgren notes, you still have to develop the idea as uniquely as you can, as well as deal with the "endless problems" that come up as you write. For instance, a dramatic plot twist that sounded cool when you first got the idea eventually backs your characters into a corner with no way out (at least, not one that's believable). Or something appears in dialogue from you-don't-know-where-in-your-subconscious that takes your character in a new, exciting direction but that also requires a major rewrite to earlier chapters. And those are just two of the possibilities.
To put it another way, ideas are easy, it's the writing that's hard.
But to quote from A League of Their Own, "It's the hard that makes it great." Because when you've made it from initial idea to finished novel or story or article, it's all yours, baby. You did it, and you alone. You got the idea, you did the work, you finished your book. Whether or not it gets published, you've done something thousands of people with "a great idea" - or, more sadly, no ideas at all - only ever talk about, and that's definitely a cause for celebration.