I've watched your video "Motivation Monday" Where I can find some more information about that?
While I can't recall the specific source from where I started that practice, I can tell you what I do.
1. I recorded my natural rhythm to find out what time of day and how was I feeling, my emotions, stress levels, etc.. Was I sluggish and unable to focus, was I hyper energized, etc.
2. I also noted what I was eating and drinking. this was to determine if anything outside myself was influencing this.
3. recorded my sleep times and quality of sleep. Again, trying to see if anything outside of me influenced my cycles.
I first did this consistently for one week and looked back on the result while continuing to record this over time (30 days) then did it again several months later and compared.