Good luck. I had a predoc fellowship from American heart association. I had to resubmit once, but in the end I got two years of full support. It's good for your career to get some support of your own. I doubt I would have the funding I have today without that experience. It teaches you grant writing, how to respond to a critique, and tells future reviewers that you're someone others thought worthy of throwing money at.
The writing about yourself part is important in all kinds of ways. It's usually not so much your "self" as your professional background and your research intentions. Some of them want to know whether you're self-reflective. Can you see your life as a coherent story? Do you have vision and substance? Are you a good investment? That's what I think they're looking for? b_b?