I sort of agree with Lari29. No offense. But the harsh reality of it is that this was the EXACT same answer my brother (who is an osteopath) pretty much threw in my face for the honest brutal truth.
However, I was in your shoes and I remember feeling the same way. Where to start?
Here is what I would recommend as to how to start these. You need to have an exact reason as to why you want to be a physician in general, and then I would incorporate the osteopathic principles as to why that approach fits in with your ideas of what a physicians is.
Another thing that I did before I began any essay, I actually brainstormed and just did a stream of consciousness essay that generally addressed my reasons for wanting to become a physician. I did not focus on any particular essay, I just wrote down whatever I was feeling about myself and the profession. Another thing that I did was I listed my strengths and weaknesses in an essay format and if this is difficult, because it was for me. I suggest that youlist your extracurricular activities first, and then look at the strengths that wer required to do those activities.
I apologize if I sounded harsh, but the reality is that (and this also applies to me!!!) if you have difficulty expressing yourself when you are given a piece of paper with an unlimited amount of time to think and research a good answer to a question, just think what can or may happen when you are in a face to face interview being grilled about similar questions. Just something to think about. Good luck!!!
Another recommendation that I found extremely useful was a book called "Essays that will get you into medical school." i read through this, it gave me ideas, but in all honesty, I did not use any of their formats with the supplemental applicaitons. it was only useful for the primary AACOMAS, and that I am sure you already finished