Facebook (when that was still a platform young people used). I would obsessively scroll through it for hours each day, basically trying to look at and comment on EVERYTHING. On a whim, I decided to take a break from it for a month. By the time the month was up, I realized I didn't miss it at all, and that was that. One of the big takeaways was that I thought that I was forming relationships with the people I'd comment back and forth with, but in reality these were people who I would never hang out with outside of school and barely even talk with in school (if at all); it was all just superficial, and I was better off spending time talking to my actual friends.
It wasn't that bad, but in high school I mindlessly got into the habit of drinking a few cups of Coke each day (I think it started because I would get a 2 liter whenever I'd order pizza). I quit it pretty much cold turkey, and not only did I stop drinking it at home, I no longer order it at restaurants either, which is something I did ever since I was a little kid. The idea of just buying a bottle of soda and drinking it is straight honestly grosses me out now even though getting a can or bottle from a vending machine was something I'd do without thinking. The one exception is when I'm pigging out at the movies with a bucket of popcorn, but that's pretty rare.
I miss before the feed existed. People would just update their page and Wall and you'd have to look around to see what people has changed (you could just see they made an update".
The Wall itself was just an insecure text box, so you could say something and identify yourself as whoever you wanted (there was no linking here) and they had no way to know who actually typed it.
I hated it as soon as the feed came out, really hated when it became open more widely (I was a college kid mad the little kids were coming to mess up the playground)
I kinda stopped using it much as soon as high schools could join. I would log in every couple months and remember I still don't care about any of these people. Then I finally made the move last year to download my data and delete the account. Haven't looked back.