Oh you can remember a lot, wether or not it's useful information is a different matter entirely

One of the homebrews I was in, the dm agreed to this:

-2 cha (because you are unreliable, and often caught up in your own mind, tho it’s not intentional it can be seen as rude)

Coordination/sensory processing issues, get a -1 dex, because why not, it would apply to me so fair is fair, and adhd sucks.

-2 con, because we often can’t remember to take basic care of ourselves, which is part of keeping healthy and fighting off disease and whatever else saves on con

But +2 to wis and int for any classes that don’t use it as a class stat (lawl, you aren’t gunna be a learned caster if you can’t study or experiment for decades! But you can apply random things you know in ingenious ways!), and +1 to all lore checks, specifically (I guess now this would be arcana, nature, religion and history? We definitely didn’t split it up like that.. just the catch all lore check)

And to top it off, at the beginning of each day I was required to remember to say I took my concentration draught. If I didn’t, everything I did had the DC raised by 1. Needless to say, I usually forgot. :)

You just can't cast verbal magic, because you forget what you were just saying

Edit: and forget about concentration spells too