Speaking of ADHD, and on a more serious note,
I'm very sorry if we know each other but I haven't reached out to you lately. This past year I've been making more and more friends outside of my core friend group, and unlike keeping up with a group I talk to every day, it can be difficult for me to remember who I've talked to recently and who I haven't. It's not my intention to neglect anyone, I'm just very bad with both remembering and having the mental capacity to maintain disparate friendships. Not to quote Radiohead but it often feels like spinning plates.
If I haven't spoken to you in a while, I promise you it's nothing personal. This is just how my brain works, at least for now until I learn to get used to it all, assuming I have that potential.