The first refers to the common Tetris problem of not having enough time to decide on the best move. It's just a special case of a larger theory, but the images of a bunch of scattered blocks piling up to the ceiling and the blinking screen when you lose have always stayed with me. In my memories, blinking screens are tied up inextricably with regret. I discovered this the first time I saw the sun set at 2 PM over the tops of buildings in the Financial District. There are only a couple hours of direct daylight in a corridor of buildings that tall, and when the sun passed over a roof and darkened the street below I realized it would be evening for the rest of the day. I looked upward and everything blinked.
The second meaning of "Tetris Effect" is a condition that can happen after doing something repetitive for too long. Sufferers feel the mental continuation of a movement even after physical action stops. I've felt the Tetris Effect after figuring out a complicated subway trip, reading Wikipedia or listening to music. The experience is never pleasant.
I've had several nightmares that involve puzzles, and I think this is the cause. Once, I twisted around in bed for hours, dreaming that I was still awake, trying to program an alarm on my inscrutable phone. In the dream, I couldn't go to sleep until I'd set it, for fear that I'd wake up late the next morning. As soon as I decided I could go to sleep, I woke up. I'd already set the alarm. I didn't oversleep.
Sometimes I worry that it happens on a larger scale and I don't even notice. Maybe I get an interesting idea, but after I turn it around in my head a few times one of the perspectives starts to repeat. Maybe that's how people become addicts.