When you applied as an undergraduate, your personal statement probably didn't make much of a difference, because undergraduate admissions are heavily based on numbers (GPAs, test scores, etc). Graduate and professional school admissions are different! Your competitors will have grades and test scores similar to yours, because most people who have the motivation to pursue an advanced degree did well as undergraduate students. As the number of applicants rises and academic budgets are cut, every year there's more competition for fewer admissions openings. How does the committee determine that you have what it takes to succeed in advanced studies? You guessed it. Your personal statement will play a determining role in whether or not your application is successful. So you know you need to write the strongest, most persuasive personal statement you can. But here are two facts you may not know. First, most reviewers will spend only a couple minutes skimming your personal statement. Second, because their job is to weed out the majority of applications, reviewers are looking for reasons not to recommend you for admission.
Often, the first draft is not the essay you originally envisioned. You might even discover that your ideas about your theme have changed as you have been writing. If you do not like the way certain sections are stated, re_arrange them. Once you are pleased with the body, make sure the conclusion and introduction still match it and complement the way you see your topic at this point. If not, rewrite them to fit the essay you did write and the way you see your topic now.