You are doing an excellent job in monitoring your BP, David. As you recognized, BP variance can be large which will affect interpretation of single snap-shot measurements as done during doctor's consultation. In one of my earliest articles, I have discussed and illustrated with numbers how this leads to considerable misdiagnoses.

In your images, even the naked eye can discern a wavy pattern, an oscillation of BP values, which is visible because you took the measurements in exact 1-minute intervals.

Heart rate and breathing also oscillate. So, there exists a little-known technique of "resonant frequency breathing" that acutely and chronically brings down systolic pressures. It requires a device that detects the HR and breathing and instructs the user to breathe such that both are synchronized. Your stress reduction efforts may have had a resynchronization effect that contributed to your reduced blood pressure.

I typically advise my clients to measure their blood pressure at least twice a day, always at the same time and ideally under the same conditions, to monitor the effects of lifestyle interventions. Their blood pressure recordings will automatically transfer to our platform, where I use N-of-1 statistical methods to evaluate the presence or absence of an intervention effect.