It is important to cover whatever period you intend to include in your personal statement because time spent planning your sequence and the method you feel happiest with will undoubtedly make the actual writing that much easier for you.
How to write a medical school personal statement: Motive _ Third is having a compelling motive. It's the underpinning of the whole essay. Unless you speak to a compelling motive, the default result from the reader's point of view is this student is writing a general medical school essay, but doesn't really know why. You've got to be willing to flaunt the motivation and be really willing to shout at the top of your lungs standing on a chair in the middle of a crowded auditorium. Be THAT committed to what you have to say. All of this sounds incredibly unrealistic and incredibly overdone, but once you put these concepts down on paper, the very act of reading mutes so much of the impact of language, that you've got to be willing to trust that you can be very committed and very over the top in how you articulate, and it will still carry off.