in prose is related to the illusion of fluency. A lot of stylistic revisions I make have the aim of fixing unwanted rhythmic hiccups, interruptions of the flow. Once again, the process of writing (how you achieve that flow) is less important than the product, or having achieved that fluency at the end. Unfortunately, few of us are fluent writers in early drafts.
Take that paragraph above, which is basically written on the fly. It's fine for a blog post, but wouldn't really cut it in one of my books. Almost no prose is as well-written rhythmically as poetry. That would be an impossible standard. Of course most poetry doesn't achieve that standard either.
I'm writing something in Spanish now to give as a talk later this month. The rhythm of Spanish prose is quite different because the information structure of sentences is more flexible and sentences tend to be longer, with more seemingly unimportant material in the beginning of sentences, so this makes me conscious of having to achieve a different sort of flow in my writing.