I’m currently feeling that loneliness. I just got separated from the Air Force for having ADHD (which the Army, surprisingly, is more than willing to try and waive to bring me back in) and it was like losing a second family that never questioned or berated me for my quirks. We were a team, and we had to bring each other up if we weren’t doing our part at 100%. I’m making friends again at my new job, but they’re not really close connections because I fear that they won’t understand what I go through. Hell, I even had one guy in my training class completely deny that ADHD existed (I laughed at that though, because if it didn’t exist, then I’m about as normal as a rat-sized elephant). Just don’t give up on friendships, as the right ones can be a boon against that soul-crushing loneliness we can sometimes feel.
Also remember this: ADHD is not a personality disorder. There’s nothing inherently wrong with you. You were just caught with the unlucky break of being unable to regulate things like attention, emotions, and impulsive behavior. But you were also given a gift of creativity, open-mindedness, and a willingness to tackle whatever comes your way with all your energy. Harnessing it is the only thing that requires extra assistance beyond your own efforts.