"Hacker News is definitely useful. I've learned a lot from things I've read on HN. I've written several essays that began as comments there. So I wouldn't want the site to go away. But I would like to be sure it's not a net drag on productivity. What a disaster that would be, to attract thousands of smart people to a site that caused them to waste lots of time. I wish I could be 100% sure that's not a description of HN."
Throw in the ease of changing direction (jumping from one article from another in a wiki rabbit hole, say), too.
What do you fill the rest of the time with?
If you accept you have a finite limit of really good productive time per day in you, it becomes easy, focus on supporting that and making sure you achieve what you can during that productive time then slack off for the rest of the day.
Thinking time is effective time. Intellectual labor isn't typing, though that's sometimes a necessary mechanism for reifying the output.
One thing I've realized over the past few years is that it's almost impossible to get away from 'wasting' a fair few hours each day. It's a good idea to let yourself disengage and move into a more diffuse mode of thought instead of trying to hold your nose to the grindstone unnecessarily. It may be that the effective people you know are that way because of their willingness to take a extended breaks rather than in spite of.
Would really appreciate this thanks
The thing with mindless browsing is that it gives you an instant trickle of dopamine. Any other activity requires some ramp up time before it feels rewarding. It's a bit like snacking vs. cooking a meal.