I see the root cause (for me atleast (used to read HN and blogs for 4 hours everyday)) is that i cant stand being with myself.
During the last two months ive been trying to not panic when i'm idle. And not take out my phone or read the nearest material i can lay my hands on.
Instead i try to accept the necesity of "falde i staver" (danish for 'falling out of presence'). When i was a kid i would often just fall into this state and just defocus with my sight and let daydreaming take over.
Basically i have a war going against effectiveness. I hold unto my right as a mammal to be inefficient and sit drooling looking at trees.
My advice on "doing something" when you have day without plans is the following: Bike in the forrest, coffee from thermos near the ocean, read newspapers at the library, talk to people at trainstations (the frequent hangouts are always open for conversations)