The smartest people are open to suggestions for improvements!
You may think your essay is done, that it’s your best effort. Not necessarily. Bring it out and have another look at it. Editing is a never-ending process. You can always find something to reword, make clearer, or support better. It is always wise to make sure at least one other person reads your essay for errors. Have an English teacher, your guidance counselor, or your parent(s) look at the essay with a critical eye. The main thing is if someone suggests something, don’t get defensive. Open up to the possibility of changing the essay. You may not follow directives exactly, but I bet just looking at it with a different eye may help you improve it.
Write for your reader, and remember; you’re not the reader.
What you think is a good essay really may not be a good essay at all. Remember that college application essay readers look at thousand of essays. How many application essays have you read? Also, application essays are not the same kind of essay that your English teacher assigns and grades. You may get all A’s on your essay in English class and still miss what the college application essay demands.
College Basics has 14 articles about writing the college essay. Maybe you should take a look.
In short, don’t be short-sighted and think your essay is done. Look at it with a different eye and take criticism seriously.