Some applicants may ramble on about themselves in a manner that may appear self-indulgent and not very appealing to the committee. Remember, this is an application essay, not an autobiography. Conversely, some applicants tend to say too little, perhaps hesitating to promote themselves too explicitly or not knowing what about themselves would be interesting to people whom they don't know. In such cases, perhaps focusing more on what you want to do than on what you have already done (let your record speak for itself) may help in getting beyond self-inhibition.
What is a personal essay? This type of essay has a purpose of revealing the personality of the applicant for a graduate education in a certain field of study. Ordinarily, the applicant is expected to include his personal history and experiences that were vital for this specific educational choice. Personal narrative essays are not limited by the instruction but the author should be very attentive to all the details revealed as an essay that tells too much is as ineffective as an essay that provides not enough information about the applicant. This essay is supposed to present the applicant’s personality to people who have never met him and that is the reason it is very important to be objective in order to make the people reading the essay understand that the applicant by no means is exaggerating.