The PS should always end on a positive note, and the conclusion should summarize the body of the statement. It is important to reiterate the primary message of the personal statement and thank the audience for their consideration. This will leave the reader with positive images of the applicant as they put the personal statement down.
Just as a strong personal statement can get you in, a poor personal statement/essay can quickly eliminate you from the mix. When a medical school committee has a few hundred applicants, seeing typos, spelling mistakes or bad content will quickly move you to the bottom of the pile. The personal statement is a quick way to "weed out" similar applicants. With two similar applications, the personal statement can decide who gets an interview and who does not.