Re: But...
I think the key is to know why you are tracking what you track. It's like performance tuning, you need to know what to measure and what to ignore.
If you are tracking it with a specific aim in mind then it can be very useful, but otherwise it just becomes background noise, and for the otherwise fit and healthy I definitely think it could be paranoia inducing.
I am losing weight, slowly, through simple calorie control and exercise. For that I constantly track my calories in and exercise, and measure my weight and body fat daily*, plotting a rolling average.
Each of the things I'm tracking is for a reason, either there's a target/limit to aim for (calories in/out) or it's a measure of progress (weight/fat %). I measure calories in because a lifetime in an overeating family screws with your sense of what a reasonable meal is, so you have to retrain your brain.
I used to wear a FitBit and use MyFitness Pal, but I found the passive nature of the data collection less useful than actively having to work it all out and record it myself. Because it required so little effort it didn't register as much consciously. Somehow having to work out the calories in a meal by hand and enter it myself seems to register more in my brain and is much more likely to make me stop eating.
Measurement is all well and good, but you have to know what you are measuring, what it means, and more importantly, what it doesn't. It's one of the reasons I plot a rolling average, it's the long term trend that matters, not the day to day weight.
* I know the number from a domestic body fat scale is dubious, but it's the change that's important)