Is it silly? Kinda!! But sometimes I just need to remember that I need to remember something later.
This card now lives in my wallet and when I'm away from home and need to remember to do something later I pull it out of my wallet and stick it between my wallet and my bum in my pocket. Then when I get home and take my wallet out I say “oh yeah I need to grab XYZ to take to work tomorrow” and put the card back in my wallet.
ADD/ADHD is a thing… we all come up with our own tricks to manage it, this is one of mine.