Although I can't tell you WHAT to write, I can tell you WHAT NOT to write.
95+% of personal statements (in IM, which is my field), fall into the following categories:
1. Why I want to do IM -- usually either for longitudinal patient care, complex patient management, or puzzle solving.
2. My own / family member's / friend's medical illness
3. Let me rehash my CV for you -- first I was the kindergartener of the year, then....
4. What I'm looking for in a program.
In addition, virtually 100% of PS's talk about a patient, even though it really has nothing to do with the PS in the first place. Apparently it has become dogma that your PS has to have a case in it, a quote, or both.
There is nothing wrong with these PS's. They just get boring to read, and don't stand out. I would suggest that you consider writing about something different. Write about something you love to do. Write about something non medical. Tell me something about yourself that's not in your application.
To be fair, this may not be great advice for the more conservative specialties.