Following your outline closely offers you a reasonable guarantee that your writing will stay on purpose and not drift away from the controlling idea. However, when writers are rushed, are tired, or cannot find the right words, their writing may become less than they want it to be. Their writing may no longer be clear and concise, and they may be adding information that is not needed to develop the main idea.
When a piece of writing has unity, all the ideas in each paragraph and in the entire essay clearly belong and are arranged in an order that makes logical sense. When the writing has coherence, the ideas flow smoothly. The wording clearly indicates how one idea leads to another within a paragraph and from paragraph to paragraph.
Reading your writing aloud will often help you find problems with unity and coherence. Listen for the clarity and flow of your ideas. Identify places where you find yourself confused, and write a note to yourself about possible fixes