Running

I started using OpenTracks a couple years ago and ditched runtastic (i keep calling that, it's been adidas running for ages) when I discovered it made my runs public, with gps data and all, for the social features of their app. OpenTracks is FOSS, I got it from fdroid, the data stays on your phone, you do what you want with it. And most importantly it only tracks your activity, just that, no social media crap.

Then again if you don't want to track your runs just don't, I personally do it because I like to see my progression and to keep notes to myself on how/what/when i eat/sleep/etc effects my runs and stuff like that

There’s no need to look at the data now, but it can help in the future.

When I’m feeling discouraged, I look at my resting heart rate trend over the last 6 months, and my vo2 max trend, and it convinces me to keep going

I used to be really keen to see my stats, both as I was running and after I finished. I've weened myself off that a bit these days, now just a quick glance at my progress etc. The key was reducing the data screens on my watch during the run. I just have distance completed, actual clock time and distance back to start.