Associating all these health markers (sleep, activity, diet) with an actual result is cool and something more fitness apps should do. Right now you can setup tracking for all these things relatively easy but the purpose of tracking them seems to be vaguely feeling "good" or losing weight. The apps encourage you to sleep a certain amount and exercise but it seems difficult to correlate those numbers with performing something you care about at a higher level.
I usually just say something like "yeah I guess I have been feeling more focused lately" but that seems pretty subjective.
The gold standard of medical evidence is the clinical endpoint. How someone feels after receiving treatment is subjective, but is is subjective per subject, so the subject in the numerator cancels with the one in the denominator, and the result is an objective measurement.
There are so many instances of people feeling they are doing well when the objective measure reveals that they are not. The Dunning Kruger effect became a meme because people are so bad at objectively measuring their own performance.
It is philosophical whether feeling you are doing good is more important than actually doing well, but for a metrics based study like the one this thread is based around I want objective measurements.
I usually just say something like "yeah I guess I have been feeling more focused lately" but that seems pretty subjective.