Dual diagnoses here, autism and ADHD, given in my early 50s.
It's okay to feel sad about what might have been, but and it's a big but - now you know and you have an explanation that you're not shit at life, you live in a world that's not built for how your brain works.
I reflect back to my younger self, but the anger has gone now. It wasn't doing me any good. I did struggle at work over the years, but now I have workplace adjustments which put me on an even level as my colleagues. These are a legal right. Access to work is a great thing, mainly funded by the government, for paid adjustments, and there are small tweaks that cost nothing.
For me, some bits are home working with lower expectations of productivity on the days I do attend the office, active noise cancelling headphones, clear instructions on a task with a follow up, bullet pointed email, regular check ins with my line manager, extra breaks for when I freeze, so I can get up and do something physical instead of sitting, getting more anxious and doing less work.
These are only some, but they've made all the difference to be. I've even managed to climb the ladder a little.
Welcome to the spicy brain club, you have so much more to offer than you think you do. The very best of luck to you.