The best way to write the essay is usually to focus on your interest for science, and to tell how it was first awakened, which stimuli you were exposed to, what you have done to develop your interest, what you gained and learned at Jacobs, and finally how all of this has led you to apply to this particular graduate school, in this particular field. You should also mention that you believe you are now well-equipped to start graduate school because of your theoretical and practical training, and that you recognize how important it is to work productively with others within a research environment.
A Personal Statement is a narrative piece describing how your character and experiences have formed you into someone who will contribute positively and effectively to not only the department but the academic discipline as a whole. This is often achieved by detailing social, educational, cultural, and economic obstacles you have overcome in your journey to get to where you are today and your future objectives. A personal statement is also an opportunity to highlight what is unique about you and how you will advance diversity within the institution.