For reference I drink 1-2 cups of tea most days, sometimes none. Have never smoked, drank, or done drugs.

For me it's a couple areas I notice:

I have a more difficult time remembering names, specific words, etc...

I used to be able to do relatively difficult math problems in my head without actually thinking about it. Now I'm likely to use my phone to calculate three digit+ sums.

I find it harder to get "in the zone".