John Hopkins has posted some essays that they liked on their website (http://apply.jhu.edu/apply/essays/). Read them over. Notice how different they are but also how they all bring the person behind the application alive by telling a simple story that clearly brings some aspect of their personality to life. None of them are about winning or even excelling. As the senior assistant director of John Hopkins admissions says, “Not only is this essay well-written and enjoyable to read, but it reveals some important personal qualities about the author that we might not have learned about her through other components of her application. We get a glimpse of how she constructively deals with challenge and failure, which is sure to be a useful life skill she will need in the real world, starting with her four years in college.”
If you can manage to write an essay that resonates with the reader and provoke some image of you in their head, you will have succeeded in bringing you application to life, assigning it a human identity. This turns your application from a list of statistics into the many facets of an interesting young person with substantial accomplishments, diverse achievements, and a bright future.
So, stay calm and remember that the essay is most about bringing some humanity to the application process. Do that first. Anything else is just icing on the cake.