How do I start writing my personal statement?

I suggest you start your personal statement process not by confronting it head on and starting to write whatever comes to your mind but brainstorming over all the experiences you have had that may prove relevant and useful when constructing the text. The way I advise to do this is taking a few days to just think about all the distinct periods, events, and sources of knowledge you were faced with during your life and distinguish between them. I usually create a shared google document with brackets for the different topics and ask students to write a heading, the facts, and all their experiences about each of them. This not only helps me get a general picture of their past actions, I also get a sense of their interests, direction, and possible future studies.