Narrative paragraphs have similar features of flow (or unity) and coherence. However, the development might be more related to the action or events narrated in the paragraph than to supporting an argument. Coherence in a narrative paragraph usually comes from the chronological order of the "story" or narrative. Similarly, a descriptive paragraph might find its development through giving a series of sensory details or of abstract ideas that describe an object (or concept or theory), rather than through support. These two types of paragraph - narrative and descriptive - differ only slightly in these respects from expository paragraphs, but the differences are still important.
Never apologize for or otherwise undercut the argument you've made or leave your readers with the sense that "this is just little ol' me talking." Leave your readers with the sense that they've been in the company of someone who knows what he or she is doing. Also, if you promised in the introduction that you were going to cover four points and you covered only two (because you couldn't find enough information or you took too long with the first two or you got tired), don't try to cram those last two points into your final paragraph. The "rush job" will be all too apparent. Instead, revise your introduction or take the time to do justice to these other points.