It's a bit like handedness for me. I'm notionally left-handed; I write and play racket sports (badly in both cases) with my left hand. But I play cricket (even worse) right-handed. And some things can be either way; when I occasionally have a go at air rifles or archery with my Scouts, I'm mostly right-handed but have to think about it, especially for archery, and have sometimes gone left instead.
With measures, I'm happy with either, but I think about distances and speed of travel in miles, so I'm always converting Audaxes in my head. My GPS reads in miles. Maybe it's partly because I still occasionally dabble in time trials, which are Imperial. I also think about my weight and height in Imperial, and my metric weight in particular means relatively little to me. On the other hand I did a science degree, which was obviously metric, and if measuring a piece of wood or whatever I'd normally use metric too. And abroad, I just use the metric system because signs, dashboards and everything else have that.
Cooking is like shooting; I can do it either way, and sometimes have to think about which one I'm using, although generally it's whatever the recipe says. I've still got the handwritten book with which my Mum sent me off as a student, and that's mostly Imperial, but obviously newer books tend to be metric. It helps that our kitchen scales have both.