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.
Same. I have two alarms dedicated to just 'washing machine' and 'call pharmacy' because I will forget those every single time and end up with no clean underwear and no medication. The only problem is when I'm in a situation where I can't immediately write something down and/or set an alarm for something, like when I'm in the shower. Then whatever I thought of will simply be lost to the void forever.