I feel ya on that one. I had four essays that I mistook 500 characters for 500 words. Good thing I reread the instructions just in time. It's stressful and irritating to realize you have to slash and burn your beautifully crafted essays, but it's easier than you think.
Start with getting rid of anything in the passive voice- a lot of unnecessary verbiage in there. It happens to be one of my biggest writing pitfalls. You'll also probably find that there are phrases and sentences in there that really don't contribute as much as you thought originally. Cut out words like "very" and "really". (See preceding sentence, lol).
When you think you've hit a wall, get away from the paper for an hour. Take a walk or a bike ride and look at it again with fresh eyes.
Good luck! Git 'er done!
Oh and the irony of all this stress (from my experience), the day after I sent off all of that (and paid the rather high app fee) I found out I got into my first choice program. Gah! Lesson learned: It'll all work out.
