The biggest bit of advice I can give to high school students applying to college: WRITE YOUR OWN ESSAY. Believe me, college admissions have been doing this forever and know when they’re reading an essay written by an adult. Be yourself, be honest and double-check what you’ve written.
Its of course. Everyone should check his/her own writing before publishing. Should go for double check in order to catch the mistake.
Have someone you trust proofread your essay. No matter how many times you re-read your own work, you tend to see what you KNOW you meant to write, as opposed to what’s actually typed.