Aim for the middle ground of polite, professional, lively prose. The essay must flow smoothly. As you revise and refine the piece, be sure it has a distinct beginning, middle, and end. Look for clear transitions between paragraphs, and make sure your sentences vary in length and structure. You can make sure that your writing is active and lively by double checking the verbs.
Many writers have trouble writing about themselves.
They loose their ability to see the essay after a while, and what they intended to display qualifications, they fear sounds only like empty bragging. You need to get good responses from several people to know how your writing strikes an audience. If ever you write an error-free essay, this needs to be it. Grammatical and mechanical errors may ruin the entire application.