The people reading your essays are regular human beings, which means you should write with that in mind. A good way to check your tone is to read your essays out loud. No, not in your head, out loud. Read them to a friend, parent, sibling, whatever, and if you feel embarrassed or uncomfortable by the style, then you should change it. This doesn’t mean you should add in colloquial filler words like like, um, and uh, but it means that the essay should flow smoothly enough that you feel comfortable reading it out loud in front of someone you don’t know very well (don’t actually do that, but you should feel good enough to).
It may sound like a chore, and it will certainly take a substantial amount of work. But it's also a unique opportunity that can make a difference at decision time. Admissions committees put the most weight on your high school grades and your test scores . However, selective colleges receive applications from many worthy students with similar scores and grades—too many to admit. So they use your essay, along with your letters of recommendation and extracurricular activities , to find out what sets you apart from the other talented candidates.