Let me be clear. Good fiction may be credible and life-like, but realistic it is not . If real cops would engage in high-speed car chases as a matter of course, all our police departments would be bankrupt. Reality would be a very weird place to live in. In return, the story promises to move the reader, thrill him, make him think, and entertain him.
Good fiction makes good on that promise.
And that's all there is to it. As a writer, you're expected to chase your characters up a tree and then throw rocks at them. Sob, and sob some more. Fine for real life, but for fiction it just won't do. Writers who allow their characters to respond realistically tend to overwrite-not good when you're dealing with a thought or two, and downright disastrous for longer stretches of thought.