YES, keep it to within 10%. The adcoms read so many essays, they can tell when one goes over that.
The essay limit sucks, but it makes you a better writer, because you have to be tight and express your thoughts in as few words as possible. You know how you tweak the wording on your resume to make it fit? Do the same with your essay.
I am lucky in this regard because I do a lot of writing for work and a lot of layout, and simple tweaks can make a line of text fit a small space. It's often just a matter of a word or two. Look for anything that's more verbose than it needs to be, and choose descriptive words that have impact.
I don't know if we're allowed to post things on this site to ask for help in tweaking essays, but if so, you could try that if you're stuck on a particular phrase.