A very inspiring contribution! Thank you very much.
Your question at the end makes me want to take part in your experiment.

As you say, one aspect of stress is to be on alert and therefore maintain a kind of stress level that is very exhausting. Always paying attention to whether what you say or do is benevolent to others, whether you give yourself professional nakedness, etc., is certainly widespread in the work environment.

Since we usually spend a lot of time working, my strategy is the following:
I work fewer hours with increasing age. I also choose my working environment more selectively and with whom I want to associate and whether the environment allows me to be relaxed or demands things from me that violate my ethical principles. So it is very stress-reducing to have a working environment that is in accordance with my chosen concept of life. Another stress-reducing element is that I no longer feel like I'm competing with colleagues (I never really have), but that I'm interested in working together and in consensus. Since the others do not see me as a threat, there is little cause for conflict on this page.

I have always liked to sleep in my private life. If possible, I lie down for half an hour in the afternoon. This relaxes me and gives me energy for the rest of the day.
Another method is that I spend a lot of time alone and reflect and write or work creatively in this time, which serve for self-reflection. It is even more stress-reducing when, for example, I already feel strained or depressed to listen to youtube videos of Buddhist monks. They ground me every time, making me calm and confident. It is a kind of spiritual sanctuary that I very much welcome.

Unfortunately I am less kind with my body. I allow myself a lot of rest and sleep as well as good and healthy food, but I should definitely have more sport and exercise. I haven't really ventured into meditation yet.

I try to encounter situations which are strange to me or which have an unforeseen effect on me in such a way that I regulate calm breathing at the moment of stress and tell myself: This moment will also pass. This is extremely helpful.

On the whole, a more stress-free life probably also has to do with self-confidence.