Focusing on negativity _ People face problems from time to time; however, there are those who have faced graver trials than others. If you are one of those people who's had your fair share of problems, make sure that you adopt a positive attitude despite the challenges, and reflect this attitude in your statement. Wallowing in negativity will give off an unfavorable vibe, and enumerating all the trials you've been through will no longer make your essay an interesting read.
Telling Them You Want the Job _ The hiring manager already knows that you want the job, otherwise you wouldn't have applied yet applicants insist on telling the prospective employer how much they enjoy their line of work and their desire to work for the company. Your personal statement should focus on the reasons WHY you should be hired, NOT why you want the job.