Decorequiem, PatientZero, I have often found myself - and sometimes I still am - facing this very problem. Unfortunately, I haven't yet found a good solution. But yes, I have been known to browse the internet for hours, indeed concerning trivial pop-cultural interests such as comic books, television shows, video games, pop music, and what have you. Off-line, I have often watched my DVDs or listened to CDs simply to kill time. And I also spent time in the library reading in encyclopedias and writing some of the entries down in my notebook, because I felt I was lacking in knowledge but didn't have a real drive to go and actually pursue knowledge intensively. Did anything that I read in the encyclopedias or books I borrowed from the library, stick with me? Sadly, most of it didn't.
I think anxiety might have been one of the reasons I was like this (and sometimes still am). Something that added to this anxiety was the feeling that I wasn't particularly good at anything at that point in my life.
But my routine itself wasn't at odds with the activities that were wasting my time. In fact, sometimes, my daily schedules were in their entirety designed for the purpose of whiling away my time. In recent months, I have made my routines and schedules less dominating, though I still have routine in my life. I felt as though I was letting my routines control me instead of the other way around, but that's a story for a different thread.
I do think a solution for the problem of wasting your time, would be to find (or remember) the things that you truly enjoy doing, and the things that truly interest you. Your free time - outside of work, school, or household chores - belongs entirely to you, so you should spend it to your heart's content. Breaking the cycle of wasteful activities may well be a bit difficult, because a body that's standing still, wants to remain still. So if you think to yourself 'I really want to be doing this or that, or be reading such and such, or visiting so-and-so place', expect that you may have to set yourself to it. It may well be worth it, it's why they call it breaking the cycle. I don't think it's supposed to be easy.
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clarity of thought before rashness of action