The body of your personal statement is going to be hard work _ you need to use around 50% of your word limit to give the admission representatives concrete evidence of why you stand out from the crowd in this application process. The body is also where you will be answering questions and giving examples of experience and affects of experience. Answers and evidence need to keep reflecting who YOU really are. If you're struggling to keep under the word limit, allocate each question a word limit as well.
The reader of your medical school application is expecting a degree of proof and really wants to know how you know. It's not enough for you to say you want to help people. How do you know what you want to do in medicine, what have you done that leads you to know that? How to write your medical school personal statement: Persuasion The most persuasive way to answer this question is by sharing experiential knowledge. You would say to an admissions official in conversation, "I know because I've done it. That's how I know. And I can give a specific story."