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.
2. Make excuses _ Lots of applicants have weaknesses in their application files, especially in their transcripts. Maybe you got low grades your freshman year. Maybe you had to leave school and work for a while. Maybe you got an F in that statistics class and had to retake it. Or maybe you got a degree in one field and are applying to grad school in a different field; or you didn't pass your medical residency exams the first time. Whatever your weakness is, do not offer excuses and do not bad_mouth anyone. So it wasn't your fault that the professor lost your final exam and flunked you, or jobs dried up in your original field of study, or you had the flu when you took the GRE. Don't say anything that sounds like an excuse or sounds like you are blaming someone else for you failing to achieve a goal. Even when it is true, it may make you seem whiny and unable to accept responsibility for your actions. Instead, address the weakness at the end of your statement, and explain how you have overcome it, learned from it, and are a better candidate now because of it.