Strongly agree with this. I’ve been using Apple’s “mood” log for about two years now, and it is extremely helpful for me to have a concrete view of the history of my general affect.

“This entire month I’ve been feeling good, I want to pinpoint why,” or “it’s clear since stressor X entered my life, my affect is lower; how can I resolve this?”

These long term trends are harder for me to track without data. It might be easy for others, but not me!