In conceptualizing a theme, you have to consider the main question, "What would you like to say with your essay?" For example, do you want the admissions committee to understand your choice of major and career in relation to your family background, or do you want to share your passion for your chosen field and your desire to achieve excellence in it? Whichever theme you come up with, this has to be unique to you as an applicant and should be related to your personal background, choice of major, and choice of career. The more unique a theme is, the more interesting the essay will be. In this sense, you can capitalize on personal facts you believe are noteworthy of exposition.
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."