After grammar and spelling, the next problem that needs be checked is transition. Read your essay. Go through it from end to end, and check to see if your essay flows smoothly. Does each sentence flow smoothly to the next? Does each paragraph flow logically to the next? Each statement should be connected or somehow related to the one before it, not thrown randomly together. Next, limit the use of "I" in the beginning of most sentences as it is already obvious that the essay is a piece written by an individual.
Now you are looking at the remaining 20% of your word limit being your conclusion. Percentages may vary if larger word limits are being offered. Ensure you state why you are interested in this field of study; state the key points from the body of your essay (e.g. accomplishments, experience and interest). Ensure that you keep it brief, to the point and leave out the clichés. Just as you started your personal statement with an attention grabber, make sure you finish your personal statement with one or two sentences that are positive and leave the reader remembering your statement while they are reading the next few.