Save the game! I had the same issue because I was terrified of forgetting things...so I've started taking notes and reminders for the following day(s) in order to resume the mental processes. Even a to-do list using todoist would free you some CPU cycles and will make you sleep better.

But the game plays further in my head even after I shutdown the computer or write down the last note. I often find myself above a piece of paper that I wanted to scribble on, but my mind jumped and run around much faster than I could even start to write anything.

I just count my breaths to 10 to stop the endless thoughts from coming up. 1 while breathing-in, 1 while breathing out, 2 - in, 2 - out, 3, 3, 4, 4, and so on until I reach 10, then I start over from 1 again. If you do this for long enough, at some point your brain will learn to do this automatically. If that's the case. Increase the difficulty. Count to to 10 then back to 1 then back to 10, etc... Or count in multiple languages. This helps me to put myself to sleep (to stop endless train of thoughts) all the time. Of course, sometimes, you need to think things through. You need to learn to recognise when this need is present and give yourself into the reflection. What's so good about this technique, is that even when I reflect on stuff, I know that whenever I notice that the reflection is no longer meaningful, I can just switch the thinking off anytime by using the technique... Hope this helps.

Take up less things at once, or, try and focus on one thing, preferably finishing it at the end of the work day. Divide your tasks up into smaller, achievable subtasks, check it off, save the rest. It's okay to not do everything, you can't.