When I'm flying by myself (meaning not with my instructor or on a check ride or something) I feel quite calm and at ease. I could stay up there forever if I weren't being charged 200 bucks an hour for the privilege (and you know, bathroom breaks).
And yet this is what my Oura Ring shows for my stress level:
That spike is when I was flying -- doing some low altitude maneuvering work around Leslie Salts (just to the West of Fremont) then shooting some takeoffs and landings at Livermore. I was at most 3000 feet up so I don't think this would be due to some Oxygen thing.
Foreflight and Oura both have APIs so maybe I can use some of my computer programming skills to match up stress and heart rate levels with takeoffs and landings.