Have you tried medication?
I would start with that.
People will say things like exercise or certain routines, etc. but nothing compares to how effective medication can be.
Everyone's brain chemistry is a bit different so this is where you need to work with a psychiatrist to see what works for you.
I still faintly remember when I started taking medication. I was also in my 30s. It was as if for my whole life there was this fog in my brain which had been lifted.
I was still in university at that time. In class I could now sit through long lectures without my mind wandering and follow along every word. I could dive deep on any topic I studied. My grades were now on the other side of the bell curve.
It fixed my insomnia. It helped me lose some weight too.
But there are some negatives.
I'm more anxious when I'm on it. Which means taking it during an exam or a job interview is a bad idea.
I'm also more likely to keep going deeper into one path without looking for better alternatives (this post is becoming a good example of what that looks like).
I still like my ADHD brain, it makes better long term and strategic decisions whereas medication is how I get through the day to day grind.
Thanks for coming to my TED talk.