Nice. I know a similar one.

A grown son asked his mother what she learned at church and she said she couldn't remember. He then complained and criticized her, "Why do you keep going when you can't remember anything? What are you getting out of it? It's pointless, ridiculous." She asked him to go and get the colander from the kitchen, which he did. Then she asked if he'd go fetch some water from the stream with the colander. "But it won't hold anything. I won't be able to bring anything back." "Yes," she said, "but the colander will be clean. That is why I go."

I like the idea that even when you're not quite comprehending, you're still getting the benefit of becoming more pure because of what is going through you.