My big thing is that I trudge upstairs to do Thing A. On the way, I remind myself to bring down Thing B when I come down. Upstairs, I see that I have to do Things C and D. Once back down, I congratulate myself on doing A, C and D. Then I realize that I've completely forgotten to retrieve B. Grrr!
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Lou and Peter Berryman have even figured out how to exploit forgetfulness.

https://www.youtube.com/watch?v=dWUygYw8gSQ