I heard an interview of a writer who said that he writes by allowing himself to either write or do nothing. He usually starts by doing nothing and then gets bored so he starts writing.

I've found that approach to be quite effective. In the evenings I also include "go to bed" as an acceptable activity. You might not get more done than if you spend the evening watching TV or surfing Facebook but you'll be much more refreshed and productive the next day.

Lastly: Banning all the "time-wasting" sites on my work machine has worked remarkably well for me.

I find the "become productive in situation x" blog posts and articles extremely irrelevant to me. Most of the time there's nothing new and insightful that I haven't thought of already. Everyone is different and motivation doesn't always come from the same source. For example, the author suggests to concentrate for a few minutes to get the ball rolling, and eventually you'll get lost in your work (hopefully). When I've lost all concentration or I'm dreading the start of a new task I usually go for a short walk or leave my work area for 5-10 minutes. I find that my work is lousy when I'm not in the mindset to work, especially when I'm forcing myself to do it.

It sounds like you've learned a rule that applies to you: to become productive again, go for a short walk.

These authors may seem to prescribe general rules since they write in an authoritative style, but we generally know to take them as considerations

This whole subject is so subjective. I once had the same views as the author, i.e. read a lot, use your time to be as productive as possible. Now I take a much different view. For example I would advocate not "diving into a book world" while commuting but instead be aware of other people, watch them, listen to their talks and try to understand their situations. The same with his 100 pages a day: I think this is also very much arguable. For most mainstream books it seems smarter to just read the summaries, for more demanding literature rushing through them makes only sense if the mission is to "hunt" some specific information down. Reading less but thinking more(critical) about it makes in my option much more sense.