What he said. I was a student interviewer during my 3rd year. Most of the essays were not impressive. I personally appreciate an honest story with smooth transitions (I'd like to follow your thought process from paragraph to paragraph) that demonstrates an true interest (dear lord please have shadowed) and an honest understanding of the profession (what we actually do for people and not what you imagine or want us to be). We don't walk on water and I don't think you do either. Go easy on the cliches. Important - if English is not your first language - have a friend proof read it.
That said - I don't particularly think there is a lot of weight given to the essay. As a student I didn't see grades or MCAT so all I had to go on was your interview and personality, but in theory I had a vote.
At DMU you are asked a series of questions. My personal experience is that people who have had more life experiences tended to have more to share. If you'd been challenged more, volunteered, or held a leadership experience then you were more likely to have something to say about success and failure.
I personally feel a lot of people who interview didn't really understand the questions. Each of the pre-written questions, in my opinion, was meant to explore your values, integrity, and depth as a person. Yes, you should answer the question, but take a moment to ask yourself "what are they really asking me". Show us some insight into yourself as a person.