Remember, your personal statement is 'personal' in nature so it is in your best interest to be sure that all the information you provide is in fact your information. By starting with one sample and taking some ideas, then moving on to another and taking additional ideas, and so on, you allow your true self to come out in the finished product and this will give you the best shot at gaining access to the school of your choice.
Check for logical flow and paragraph transition which make the statement strong and easily read. _ Read the personal statement over _ if you need to read any of the sentences twice, and then re_structure them. Have I left myself too short on an important area and too long in another? Cut and chop away until you know that this statement is strong, logical and captures the attention of the reader. If you step over a platitude or cliché _ remove and find another way. At the same time _ give yourself a limit of how many reviews you will do, otherwise you will keep chopping and changing losing the essence of what you are writing. _ Lastly, peer review _ a person or people you can trust to be brutally honest and who knows you well. Preferably someone who also understands that this personal statement is for admission to graduate school. Get several people to give you a boredom rating along with a rating of whether or not you have truly reflected who you are.