Actually, I use contractions for personal essays I submit all the time. There is a difference between formal and academic writing. I was taught the no contractions rule applies more to academic writing than formal. However, in high school I was never allowed to use them. I am not saying you should use them in your personal statement but to say you should never use them in a paper that you submit seems far excessive. You learn the rules and then you break them. For instance, an essay with a well placed swear word can be extremely effective even if that would technically be a violation of writing rules. (However, this would be a TERRIBLE idea for a personal statement) No technically you should not use contractions but this isn't an academic paper is is essentially a themed-personal essay. As long as it is well-written I highly doubt an admin is going to judge an applicant based on their use of contractions.