Mysteries beyond human comprehension

A week or two ago a priest in my parish gave a homily about the Holy Trinity. He referenced a story from St. Augustine of Hippo (you should check the background on that guy, interesting stuff). St. Augustine was practically tearing his hair out trying to get a handle on how the Holy Trinity really works. (I have no idea how it actually works, I've just always envisioned it as a sort of spiritual tag team, a symbiotic relationship)

He came across a girl who was repeatedly taking buckets of water from the sea and emptying them on the sand. He asked her what she was doing. She said she was trying to empty the sea. He told her it was a foolish idea. Then she said to him (something along the lines of) "how do you expect to get such a big idea into your tiny head." And then she disappeared.