"No matter how wonderful the story, it has to move on something, and that is language. The words that I use, the pace, the rhythm and cadences all need to be there. If they're not there, the story is like a boat that just sits there and doesn't move on the ocean." —Tim O'Brien
Y'all, this man knows what he's talkin' about.
I've been studying his style lately, and he clearly takes this rhythm business seriously. And you know? For good reason.
How a story reads—meaning how it flows—affects our enjoyment of the piece. It could actually be one of those "make it or break it" elements.
Think about it in this light. You're sitting in a conference. A man walks out on the stage and begins to speak to you about a new scientific breakthrough that's supposed to be lifechanging. You're all geared up to have your mind BLOWN.
Sadly, he's about as engaging as the guy from the dry eyes commercial. He drones on and on. And on. His monotonous tone has lulled you into something akin to lucid dreaming. And you soon are startled "awake" and realize that you've missed the big reveal altogether because you were daydreaming about that commercial where he's holding the beachball with sand on it and pouring the "eye drops" on the ball but instead of the sand washing away the camera zooms out and the beachball isn’t really a ball at all but the eye of a dragon and…
In writing, the equivalent of a monotonous and boring speaker is the author that pens all sentences of the same length and with the same syntax.
So if you find the flow and cadence of the story is a tad…boring, to be perfectly blunt here, then a suggestion would be to mix it up a bit. Vary the sentence lengths.
But that doesn't mean to just go all willy-nilly, eeny-meeny-miny-moe on the job. There's an art to rhythm. (Of course there is!)
Match the mood.
Think about how you speak in terms of your moods. Pissed? You speak in short and direct sentences. If you are in love, you're likely to use all your eloquent imagery skills to immerse the listener in the moment you shared with your lover and may tap into literary elements such as alliteration and metaphor to relive the visceral sensations you felt with the most touching details. If you are afraid or anxious, maybe you speak in bursts of running, out-of-control, emotional ramblings. Or just fragmented lines. (I promise, you grammar nazis, it's okay in fiction to use fragmented sentences. Really.)
Apply this same logic to writing. Match the tone of the story, of the scene, of the setting, of the dialogue. It works.