Another Set of Eyes
It's always helpful to have someone proofread your essay, because another set of eyes can catch typos, grammatical errors, and other small problems in your essay. As the author of your essay, you can sometimes become blind to obvious errors because you have read it through so many times (and are probably sick of it by now)! Just be sure that proofreading doesn't extend to more substantive changes and edits to your work. Remember -- it's your work and your voice that admissions officers want to hear!