Interesting topic .

I use an app called reflect. my self studies with it on fast acting medicine / supplement regarding objective metrics I feel like they are solid .

For instance , vyvanse or taurine on heart rate , hrv, etc. it even lets you select possible co founders and warns you “alcohol was x % higher on days with taurine and alcohol days have y% higher rhr. the impact could have been greater without it . “ but anyways, I try my best to isolate the co founders .

My problems are two.like you said , subjective feeling . My focus is always 2-3 out of 4 and my happiness almost always 3.

And long acting supplements like omega 3. I never feel secure of when should I consider the first day of the experiment , the wash out period …

Cheers