I still suffer intermittent stomach aches, especially in the early hours of the morning, and had a terrible time trying to decide if they were getting better or worse over time.
Our narrative voice is awful at detecting long term trends and tends to overcompensate for particularly good or bad patches so it was impossible for me to judge and I started keeping records of how bad the aches were each day.
Long story short, the average severity was mostly decreasing over time and the average time between bad aches was slowly increasing but it would have been impossible to tell if this was happening without keeping detailed records because it wasn't consistent - some months were much worse than others and completely skewed my perception of long term trends.
While most people hopefully won't ever need to do something like this, it did make me realise just how bad we are at picking up on long term trends so I can definitely see keeping daily records of, for instance, average daily happiness being eye-opening.
Proactively capturing and tracking everything you can to prep for any future is too much work that would really steal your time from, you know, actually living a life.
I've gotten deep into weightlifting/bodybuilding over the past couple of years, and that's the kind of hobby where micro-optimizations and data tracking can have a pretty big impact on results (and sort of necessary, you can't fly blind with things like diet, especially)
E.g. I track and weigh everything I eat, take body measuraments on a weekly basis, Dexa scans every few months, etc - for me it's worth it because I know what I want to do with the data. If I didn't have a goal, all that tracking would clearly be overkill.
I've been weight lighting for ten years and initially tried to track things (down to how many reps I did of which exercise, with how much weight) and quickly came to the conclusion that is want worth it for me.
Tracking scale weight is difficult because shifts in water weight and hydration can swing the scale 5+ pounds in either direction without any change in body fat. So I pair scale weight with a 7-point skin caliper measurements taken on a weekly basis, along with waist circumference, in order to infer whether body fat is trending up or down. And also take weekly progress photos of 6 angles/poses with consistent lighting, which I share with a coach.
And then you pair that with weighing and logging everything you eat, and you can make small adjustments to your meal plan on a monthly basis to try to stay in that 200-300 calorie per day surplus for as long as possible. (Although most bodybuilding coaches adjust diet based purely on how your physique is changing in weekly check-in photos without the need for measurements, but I like extra data)
> down to how many reps I did of which exercise, with how much weight)
I also do this. Track every exercise, every weight, number of reps. It's necessary for knowing whether you're progressively overloading over long periods of time. Progressive overload becomes harder to measure once you're past newbie gains because you can't increase weight every week, so some weeks the goal is just to squeeze out an extra couple of reps. Which adds up over time
This is obviously excessive for 99% of people. But I enjoy doing it as a hobby. I would absolutely not recommend this level of tracking for health reasons (not necessary) - I find enjoyment in the process.