Okay, this will not be nearly so eloquent or understandable (by mere reasoning of being written by a neuro-atypical) as the spoon theory, but let me try.
I view my brain as a set of computer processes. Most of the time, it is a multi-threaded system that is prioritized. There are a lot of threads, but they all have their own functions and even if there is a lot going on, I can make sure they are doing what they're supposed to and that things are prioritized, sorted, and functioning properly.
There is the constant steady train of thought.
There is the music and/or ear worm that helps keep everything else orderly by setting it to a soundtrack so that nothing gets too loud or out of step.
There is the on-going task list.
There is the daily cron (wake up, hygeine, eat, chores, etc.).
Everything is multi-threaded: 'dinner' is a task that is broken down into other tasks (make meal, clean kitchen as I go, eat...), but it falls under my daily needs.
Something new can get properly added into the stack where it needs to go.
Some things remain 'background noise' unless a sub-system brings them to the forefront, like driving. Driving is driving unless a sub-system says 'Shit! This asshole is about to cut you off, put everything else on hold and deal with it.' The general noises of the world (birds, office conversation, air conditioning) are background noise, but a fire alarm isn't.
For someone with ADHD, you may have more threads than most. And sometimes keeping them sorted is difficult because things like to cross-threads or miss-prioritize themselves. And sometimes those background threads don't stay background. The average person can look at their stack and go 'You belong here' while the ADHD person goes 'haha fuck the stack.'
The problem is when the 'executive function' program faults. And that's what happens to me now. The 'executive function' program is what keeps everything threaded and prioritized. When it goes into fault, everything becomes unthreaded and everything becomes priority 1. Which means nothing is prioritized. Which means the air conditioning? Is just as loud as the fire alarm.
Which means the kid on the side of the road is just as important as the person merging in on top of me.
Which means watching a YouTube video about a sport I don't give a shit about is just as important as taking a shower (which I didn't do last night).
Which means my usual cron to check the gas in my car twice a week fell out completely and I may not have enough gas to make it to the gas station (I rarely get below a third of a tank).
I have coping mechanisms. I have coping mechanisms for my coping mechanisms. Almost everyone I've ever dated and many of my friends have made fun of me, a lot, for my lists and my reminders and my calendar apps, but when the executive function program fails, none of this matters because the instant I see a reminder I go 'cool' and then my sleeve itches and you know what happens to that reminder?
It's off the stack. Only what is currently on the very top of the stack matters because there are no threads. And this, this is why atypicals get so frustrated when other people try to explain to us 'how' we should be because of some book or article they read. Because until you're in this place, you literally cannot understand it.
I was once on a medication that treated OCD. I didn't know I even had OCD (and even laughed at being diagnosed with it) until I was on the medication. I had become so used to living with it that I didn't even know a difference was possible. Doing things like holding conversations while rearranging other people's bookshelves was just so normal to me and, by my reckoning didn't impact my life that I didn't realize the severity of the impact it had until I no longer had the compulsion. Even now, some 18 years later (the medication isn't in the US anymore so sadly, I don't get to have it anymore), I can only think of those couple years in abstract. My OCD, in my mind only affects me marginally that I barely consider it an impact. But I know it DID to the point that those two years were a wonder and an amazement and like a breath of fresh air.
So please, for the love of everything that is holy, do not tell people with ADHD, depression, OCD, etc., that it's just a matter of 'thinking differently.' Because I motherfucking assure you that we already do think differently than you do.
(btw this post only managed to get written because I spent my entire commute thinking about it, nonstop, nearly missed my bus stop, then sat down to begin drafting it immediately upon getting to work... because I knew if I began thinking about ANYTHING ELSE I would forget about it. You're fucking welcome.)