I think an important thing to keep in mind is not simply to list your experiences. Your personal statement should not read like a CV. Instead consider it a chance to delve into why you want to be a doctor, not how you have prepared to be a doctor. This is tricky and requires serious contemplation, but if done well it can convey a real understanding and passion for your future profession. It took me a lot of time and I did a lot of revisions until I felt I got to that point, but in the end it made the interviews a lot easier, because I had already answered the big question "Why do you want to be a doctor?"
Good Luck!