You don't need to write to the world limit. Quality, not quantity counts. In fact, less is more. Keep it tight, make sure that you have a strong lead--a good hook to grab the reader's attention.
Keep the tone clear, honest, and natural. This is not a technical paper. This is a personal statement. Don't be cute. Don't be flowery. Be concrete. Be creative.
Show don't tell. What I mean is: Use narrative examples, be specific. Don't say you're a compassionate person. She us by telling a story where you showed empathy, compassion.
Don't let the piece fizzle out at the end. You need a good closing, a summation, where you sell yourself. A good device is called an Echo Effect. You introduce a word, a theme, or an idea in your first paragraph and then you revisit in your final paragraph, but it now has a new twist. Get it?
Good luck and have fun with it.