I typed my intrusive thoughts in to a document and analysed them. It turns out I had a hundred of them. It really helped to write up why they don't matter now,

I typed my intrusive thoughts in to a document and analysed them. It turns out I had a hundred of them. It really helped to write up why they don't matter now, such as "I was a child when that happened, I'm now an adult who knows how to handle that." My brain thinks that a physical piece of paper is much more authoritative than a thought in my head and makes less effort to remember things that are documented so having twenty page booklet that I can get out if I need it seemed to help.