I've found the single best measure of my stress and anxiety levels (as at their worst, my subjective perception can't be trusted) is HRV during sleep. My Garmin watch tracks it, and when I actively try to manage stress and anxiety during the day, it goes from red (for weeks) to immediately recovering into the green that night. I like a good dataset and the correlation with my stress (backed up by papers on causation)…
which garmin watch do you use?
Forerunner 255s