A personal statement provide professional programs the opportunity to learn more about you. Each type of application has different length requirements and a slightly different question. Basically, however, they are trying to get to know you a bit more and discover your motivations for wanting to enter that particular field. Remember, this is their first interaction with you. So be yourself and give them the opportunity to get to know you.
This is your opportunity to expand upon your experiences or to address anything that you feel has not already been covered in your application. Remember, however, that they are trying to get to know you. The essay, as much as possible, should give them insight into you. How have various experiences motivated you and changed the way you view the world? What unique qualities do you bring? What have you gained from various experiences? Saying that you are a very empathetic person isn't really helpful. You need to give them concrete examples of how this has played out in your life.
Remember that most applicants are generally really well qualified. So do not underestimate the time it takes to write your statement or the importance of it.