The personal statement is also a great place to explain more serious problems, like less_than_ideal grades or test scores. Don't be afraid to write something like, "I don't test well" in the statement. As long as you can provide a good reason for you app's problems, it's okay to address them directly. You won't be able to hide it from admissions officers anyway, so providing a reason for problems is always preferable to ignoring them.
Stay Focused on your Theme. Before you begin your personal statement, decide what point or theme you want to get across. Make sure the entire essay revolves around that point by editing out any sentences that may lead the reader astray. Though you may be tempted to share a lot of different information about yourself in order to give the admissions committee a complete picture, it is more effective to highlight one revealing, important aspect. Pick something about yourself that you feel makes you stand out from the crowd and is related to your decision to become a physician.