Unwanted paragraphs or even sentences in an essay are not good. This is why it is important to think about "all paragraphs and sentences for the greater good of the essay." Because the audience of the essay is someone who wants to grade it quickly and accurately without any problems or distractions, it makes sense to focus on unity and coherence.
Every topic sentence should set parameters and boundaries for the discussion. Each and every sentence should develop the initial idea. When a sentence strays off topic, the momentum of the discussion is lost which can lead to a lower score. Not being able to comprehend an idea in the essay easily is bad for the grader.
Thinking the essay through before writing anything down is a good idea so that a structure can be formed and stuck to throughout the essay. This can help avoid getting off topic and lowering the score on the essay. More examples are not necessarily a good thing. Choosing the very best examples is a much better idea.
A well written paragraph will show both coherence and unity because all sentences support the main topic sentence. Also, the sentences follow in an order that is logical and that helps enhance the topic.
