As you write, question the meaning of everything you write. Ask yourself if your meaning is clear with fewer words or phrases, or if you are repeating yourself. Concise prose is tough and convincing.
Wordy prose is boring.
The quality of your writing affects your grade. Poor writing makes it hard for me to be sure that you know what you should, or that you understand what you know. You demonstrate understanding by putting relevant facts together in a way that increases the sum of your knowledge about the topic. The organisation of your essay is as important as the words and grammar. You will need to select the most significant items from this material and arrange them in the manner most effective for discussing the topic you have chosen.