What I did when drafting mine, and I'll admit it will probably be worked and re-worked before I apply next summer, was write from the heart. What did my story want me to say, because we all have one. I didn't worry about what the adcoms will be looking for. I didn't worry about the prompt. I didn't even worry about how long it was, if it was 5,000 characters or 20,000. I just wrote. I wrote for as long as I wanted to say what I needed, and once I had that, then I was able to sleep on it and then see where I was missing x or where I could cut down on y etc. But I honestly think that the first thing you need to do is close your eyes (either figuratively or literally; sometimes literally actually really helps me 😛) and write. Everything that led you to this moment, everything you'll aspire to in the future, write, let yourself feel it in your chest as you write. And then you can worry about everything else. But I definitely would start without worrying about what you sound like, without worrying how long it is, and write down everything you would say if you could write an unlimited amount and submit your very roughest draft.
