In my experience my parents issued blanket bans and the threat of punishment for eating sugary foods, using the internet and watching TV. All this did was cause me to binge on all three whenever I had the opportunity at a friend's house, and that behavior extended into my adulthood until I was able to break free of my parents and seek the advice of reasonable adults to help curb my addictive behaviors.

When I discussed this with my parents they doubled down on their behavior, washed their hands of responsibility and blamed me. They used the same tired "how you behave when you are an adult is up to you" line. I hope you aren't doing the same to your children.

I take the somewhat contrarian view: kids (at some age) need to learn to cope with absolute limits that are strictly enforced. How else will they cope with living in real society? Not paying your rent will get you kicked out. Driving over the speed limit will get you a ticket, or worse. Not showing up to an exam in college means you fail the class.

Not saying you should have draconian rules on everything. But some rules need to be enforced with (reasonable) consequences. Otherwise you are doing your children a disservice, IMHO.

My kid has limited screen time that is strictly enforced, roughly 30 minutes a day. They're well aware of this fact and when it will happen.

We occasionally make exceptions for things like movies or what have you on the weekends.

This is not binary. As they grow older, kids should be able to take control of their lives more and more. Probably much more than the average parent thinks they should.

Edit: To clarify, I don't mean kids should become more skillful in controlling themselves according to their parents wishes. I mean the parents should gradually micromanage their kids less and less as they get older.

Indeed. It's strange to me that people try to do things any other way. At the start, you have a tiny person who has no idea how to function in the world and is entirely dependent on others. Somewhere around two decades later, you have someone who needs to be ready to go out into the world on their own and operate independently. How else could you possibly get them from one to the other effectively if not by introducing more freedom and more responsibility over time as they become mature enough to handle them?

Probably the biggest complaint when I've spoken about childhoods with friends of my own generation, and the thing we pretty much all agree we want to avoid with our own generation of children, is strict and arbitrary-seeming rules that remain in place for far too long. Obviously no five-year-old is ready to make their own fully informed decisions about everything. But a fifteen-year-old? Hopefully by then they'll be making most decisions for themselves and relying on their parents more as advisers and a safety net than as figures of authority.

I've read stories of folks successfully getting their kids to manage their own screen time.