Personal Religion stuff
I have a strong relationship with The Goddess. I grew up in Her temple, learned Her rituals, and looked Her in the face on a February morning standing on a seaside cliff, suffering Her moods while making the most pathetic efforts to keep a cliff face from being washed into the sea.
So it's not so much Belief as Experience. I know she's there, I got taught her magic growing up. It's still what I'm best at.