As a young child, I routinely took home a foot-high stack of library books, read them, and returned for a new stack the next week. I was writing A+ stories long before a teacher showed us how to diagram a sentence. I still read and write - but I don't diagram sentences. I write according to the sound, the flow, the feel of the words. If a fragment works better than a grammatically correct sentence, I use the fragment. I use paragraph breaks the same way - according to what fits the flow of language.
Some people are fanatical about every sentence being grammatically correct and/or any of a wide range of rules someone has told them are essential to good writing. So, as I read Stephen King's On Writing, I was very happy he says (on p. 134) that "Language does not always have to wear a tie and lace-up shoes" - that the author hears the beat as they write and that determines where to start a new paragraph and when to use a fragment. He explains that "beat is part of the genetic hardwiring...but it's also the result of the thousands of hours that writer has spent composing, and the tens of thousands of hours he/she may have spent reading the compositions of others."
Read that one more time - make sure you've put in those hours of reading and writing. Once you have, trust your ear and listen to the beat as you write.
