Writers love their work, or they wouldn’t be writers. The problem is that writers also tend to love their characters and plot devices, even when those things don’t stand up to close (sometimes even casual) scrutiny. Reviewing a manuscript provides with the invaluable opportunity to put every aspect of your work to the sniff test, using common sense to check the believability of a plot device or a character’s behavior.
Believability is really the key to this test. A common horror movie trope has the victims exploring the boarded up house in the middle of the night, even though they are fully aware there is a killer loose and their flashlight has just run out of batteries. This seems so unlikely as to be ludicrous in any story that attempts to take itself seriously. While it’s true that panicked people can and consistently do make exceptionally foolish choices, this one just isn’t within the range of possibilities. It’s not believable. It doesn’t pass the sniff test.