My two cents...just write a 'statement'. Put everything you can think of in it -- your situation, experiences, why you do what you do, what you like people to get from your work...everything. Don't worry about length nor grammar, etc.
Then start eliminating stuff...distill it down to what you want to say and to what people will actually take the time to read (perhaps 2 or 3 paragraphs of 2 to 4 sentences each).
I spend a lot of time on mine...some approach poetry. But no one has every commented to me about any of my statements. I write them for me, now. It is a good exercise.