I'm sorry you're struggling with this. I don't have the type of problem you have such as with numbers. But I do find it pretty-much impossible to let go of the past. So I can certainly relate to that. How I handle intrusive thoughts, as well as anger (which I also have a lot of), is through the use of the practice called compassionate abiding. Here's a link to a description of the practice:

Relieve Distress By Allowing It: Compassionate Abiding 101 | Mindset: Perspective Is Everything

And then here are links to 6 articles, from PsychCentral's archives, on how to let go of stuck thoughts:

9 Ways to Let Go of Stuck Thoughts

Some Ideas to Help Stop Obsessing

7 Ways to Stop Obsessing

9 Ways to Stop Obsessing

https://blogs.psychcentral.com/relat...-event-1-of-2/

https://blogs.psychcentral.com/relat...dium=popular17