Here’s one way your story can get bloated: start either identifying with or sympathizing with your characters, and then start to like them. Then if you don’t like them, appreciate their vileness. And if their vileness is too vile to be appreciated, then appreciate the fact that they are either a dark mirror to the protagonist or a light-absorbing example of how low one can sink.
Becoming enamored of your pretend people after a certain level of detail and setting poufs the page count to heights better left looked at, not ascended. As a firm believer in the “less is more” theory, this is the literary equivalent of drug addiction. You now have character addiction.
Character addiction is insidious and painful. Painful because while self-editing you start to chip and cut into their existence because the story is drifting. Lord help this now wounded thought-soul when a real editor gets your work. Now one of your creation is externally tortured. It hardly is fair and it certainly is not sporting.
And then, then… then you realize, this person is going to die because it is not just your characters which seem to live and breathe, but the actual story itself. The story is moving in a direction that bodes ill for your thought person. Now my beloveds are in peril, and I feel helpless to save them. One of them dies and I am left with a melancholy that hovers over me like the ocean mist on a spring morning. The mist might burn off, or it might just rain.