More seriously, ADHD, among others, is a working memory disorder. A way to cover this is to use "prosthetics" for it, such as a notepad that you always carry with you. If this affects you strongly, train your muscle memory to use it to note down what you were planning to do and to refer to it when you forgot.
In PC-speak, ADHDers have traded RAM for more CPU.
This app has been a lifesaver for me. It's still taken time convince myself to use the damn thing, but the snoozable pop up in your face reminders has helped a ton!
https://play.google.com/store/apps/details?id=alarm.clock.calendar.reminder
Love that pc analogy! 🤣