Good writers define reality; bad ones merely restate it. A good writer turns fact into truth; a bad writer will, more often than not, accomplish the opposite.
Unlike life, you've got more or less complete control over what's going on in your stories. That's not to say you can make characters do whatever you want them to - they usually have a life of their own if you've done your job properly.
Any dog, you put him in the corner, no matter if they're vicious or not, they're going to bite back.