The biggest story is our view of the world. We might favour one political party (with their Big Story) because we like the sum of its policies (the Small Stories). Others, might accept the policies without further ado merely because they like the party.
There is a power in telling a story in the first person. It’s only you who can share this story from this perspective, which gives the appearance of authenticity and means the story cannot easily be challenged. You also know enough about yourself to guarantee plenty of supporting detail.