I turn off all notifications apart from messaging apps, and I use a smart watch to "screen them". I noticed I had a bad habit of getting a message, picking up my phone to see if it's important and then mindlessly opening Reddit/HN and getting stuck there.

Now I just glance at my wrist, decide if I'm going to respond or not (or just reply with "Yes" from my watch), which limits how much I get stuck on my phone. I wish I had self-control to not have to "hack" around it, but alas I don't.