Boo! Want to know what's scary? Bad photo editing.
Now we're not trying to come down on anyone here - we've all been there and we've all created layers that we later regretted. It's how we learn, and that's okay!
But what's better than learning from our mistakes? Not making them in the first place!
One common editing indiscretion is to overdo things a bit. It happens. We learn a new skill, we get a little carried away, things happen that we're not proud of. Over-blurring a background is one of those things. We all love a blurred background and sometimes we don't get as much blur in the original image as we want and that leads us to editing. Which, again, is fine. What we have in our sample photo below is an image that has had a little work done. The before photo is just a simple, unaltered photo while the after has had a mask and blur filter applied in Photoshop (the same could be done in Lightroom with the blur brush). What we get when we get too excited with our editing is a ghost or glow around the elements of the photo that have not been blurred which just looks plain unnatural (or perhaps supernatural).
The solution? Just don't go in so hard with your blur - it's really that simple. There is a break point as to how much added blur an image can handle, so add a little at a time and don't be afraid to dial it back. Sometimes in editing you have to go with the lesser of the two evils: Do you want to settle for a little less blur than you wanted or do you want ghosts? (The answer is the former not the latter - Nobody wants ghosts).