Empty Words _ Since most personal statements are about 5μ lines, you don't have space for empty statements such as 'I am a hard worker' or 'I am a people person'. How can the hiring manager ascertain that this is the truth without any evidence to back up such lofty statements? You need to give them examples of your work ethic and how it positively impacted your employer as well as evidence of your interpersonal skills.
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.