There’s an old axiom: “drama is conflict”.
Without conflict, you have two guys in an empty room with nothing interesting to say or do. If you want a story, you need to get the two guys mad at one another. Allow me to clarify with a charmingly folksy definition of conflict: One guy (let’s call him “The Protagonist”) wants something. Another guy (let’s call him “The Antagonist”) doesn’t want him to have it. The Protagonist takes action to achieve his goal. The Antagonist will have none of this, and does everything he can to block our hero. Eventually, the Protagonist either succeeds or fails, and the whole thing comes to a (hopefully) satisfying conclusion.
The tug o’ war between the Protagonist and the Antagonist is the essence of conflict, and thus the essence of drama, and thus the essence of plot. Of course all of this is a grotesque oversimplification, but it is, I feel, a reasonably good definition of the plot mechanic.
Simple, right? So, why did it take me two essays to reach this conclusion? Well, I’ll tell you: I’m not good with conflict. I have a tendency to avoid it in real life and that impulse, sadly, carries over into my fiction writing. But here’s something I’ve been telling myself lately, and I’m coming to believe it’s true: At least in terms of crafting plot, Politeness Doesn’t Pay. If everyone’s getting along, then what you have is a boring, stillborn story. Make your characters mad at one another, have your hero want something and take it away from him; then you’ve got something. Do you want to craft a good story? Be mean to your hero.
Here's the best example I can think of of that particular notion: 1981's Raiders of the Lost Ark. in that film, archaeologist Indiana Jones has the ever-loving shit kicked out of him. He achieves his goal of keeping the ark of the covenant away from the Nazis, but he nearly dies in the attempt. He's thrown into a pit full of snakes, he's drug behind a truck, he's shot, he's beaten senseless by a monstrous German, nearly drowned, and nearly flambeed by the wrath of God. In short, he is a serious man. Steven Spielberg, George Lucas, and writer Lawrence Kasdan were mean to him and, I for one, love him for it.