Try this: when you have an intrusive thought/flashback, don’t hold it too close or shove it away. Having flashbacks/painful thoughts is not a “bad” thing, don’t fixate on reprimanding yourself for thinking about it. Acknowledge that the thought is there, and that you feeling it is out of your control. Now, gently put the thought aside, and let it sit beside you. You don’t necessarily need to find a distraction when doing this. You simply just need to a) acknowledge the thought, b) refuse to pass judgement on your thought or yourself for thinking it, and c) set it aside, and let it stay in your mind’s peripheral vision for as long as it needs. Let it leave when it wants to.

This will be very difficult at first, but working on your brain is like training a muscle. The more you do it, the easier and faster it becomes. Intrusive thoughts will never stop, but we can change the way we approach them. Eventually, with practise, you should be able to complete the above process almost automatically.

I hope this makes sense, this is how this process of neural re-wiring was explained to me. It seems like of like some fluffy BS at first, but with time it definitely worked for me.