This serie is particularly interesting for one key reason (major spoiler): the angels have powers. Increadible powers.
Like, invincible, wings, etc
But only if they believe they do. If they believe in themselves.
And studies have shown that we work in the exact same way!
So what do you think you can do will limit what you actually can do.
This ties back to A story is a deal which explains how we live in the story world.