I disagree - that just leads to learning to distract oneself. The most effective method in my experience is to do nothing instead of the thing you want to stop doing. Literally, stop the thing you're doing, do not transition into doing anything else, and then do nothing. For a good while. Give it an hour or two.

This is based on the theory that the REASON you keep checking your phone, HN, etc. is that you are compulsively anxious about "missing out" on information, so your brain seeks it at every opportunity, and the Internet and its services have an unending supply. The antidote is to PROVE to yourself that the compulsion is illusory, and nothing bad happens if you resist it.

Over time, you can extend the time between these checks longer and longer, and begin to notice that it's OK to miss even MOST online content, really only occasionally and with INTENT stop to consume the stuff you ACTUALLY care about. Unfriend Facebook contacts that have nothing real to say. Unsubscribe from everything that doesn't truly interest you. Set your phone on 'Do Not Disturb' outside business hours.

YOU decide what content and when you want to consume. Never browse feeds nor recommendation engines. They are intentionally tuned to be as addictive as possible, to keep you hooked, to serve you more ads.