When I was in secondary school, it was far away from my hometown, so I had to take a special bus/taxi service there. The problem was, the taxi service was crapbuckets, and they'd often NOT send a bus when I asked for it if I had the last couple of hours off. So sometimes, I had to wait for 45 minutes or 90 minutes at school, when school was OUT for me.
In those long long minutes, I had to occupy myself with something, and since the school had no library (and it didn't occur to me to bring stuff with me I could do to pass the time... peculiarly), I would play one of my favourite songs in my head, to pass 4 minutes. And another song to pass the next 4 minutes. And another. And another.
Hell, sometimes, I even specifically learned the lyrics to a song I liked (but didn't know by heart), just so I could add it to my internal jukebox (because playing a song in your head is a lot harder if you don't know the words).
Even to this day, I wile away my more boring hours by playing my favourite songs in my head. I do it on the street while walking anywhere whenever my discman's batteries are empty or I don't feel like wasting them.
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clarity of thought before rashness of action