"When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up." - C.S. Lewis

This is a near neighbor concept that I consider important to distinguish. I don't think this is a case where it's a good idea to embrace the contradiction of calling it childish to worry about childishness. Then you get into slap-fights about whose worry over maturity signals greater immaturity.

You should just be asking some other question instead - cutting through on some other question that isn't about maturity or childishness.

I quoted "Shinji and Warhammer40k" first and foremost because it had a couple of good quotes, worth adding to my quotes file and then worth selecting. The dark delight in quoting anime fanfiction comes after the simpler deed of asking "Is this a good quote or not?"