“One of the classic rules of coincidence is that fate — if it must be present — should always favor the antagonist. If our hero has a gun on the villain and the hero’s gun jams, it’s called drama. If the villain has our hero dead in his sights, and the villain’s gun jams, it’s called a lousy cheat, a not-very-inventive way to sneak the hero out of his predicament.”
Screenwriter Terry Rossio (Shrek, Pirates of the Caribbean)
And if you don’t believe Rossio, here’s a similar quote:
Note: Both quotes pulled from the 2013 post Screenwriting & Coincidence 2.0.