I group my things into imaginary categories, for example:
Hygiene Category:
. Shampoo
. Hair brush
. Tooth brush
. Tooth paste
. Antiperspirant
It takes me a few minutes to think of everything in that category when it comes to it, but regardless of how overcautious I am, I always end up forgetting something crucial or anticipate something incorrectly, where other people never do.
I believe it is primarily an executive deficit with planning. From the example I've given, it may not seem to be executive dysfunction as it appears to be a simple issue, but extend the underlying problem to everything in life and you've got yourself a huge abnormality, and one that is never really positive.
I have OCD, and it's incredibly stressful when I'm literally obsessing over these things, and I end up screwing myself over anyway.
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Unapologetically, Norny.

-chronically drunk