Focused but not concentrating

This describes several of the things I've done in the basement. Both very zen.The first was the darkroom. It was quiet and dark and you had to pay attention to what you're doing. It didn't require much concentration however; you don't get mentally tired from it.Now I have reloading. It's a very similar feeling down in the basement as I had in the laundry room of the apartment (same thing really). It's something that when you're doing you have to be there doing it. You can't be mentally off somewhere else.I can load rounds for hours and I come up refreshed.How odd is that?