I think it's possible to 'defuse' a trigger. Right now, I'm being triggered by 'book-keeping' - I need to keep books for my business, and I need to get them up to date (what with the end of financial year and all). I'm working through the process.
A few weeks ago, I would think about doing the book-keeping, and I would just shut down. Headaches, walls of static in my head, a full-on Freeze response. I could make no sense of it whatsoever. I am currently (slowly and painfully) teaching myself that its OK to think about the book-keeping - that I don't have to DO the book-keeping (yet) just because I happened to think about it.
A few days ago, I was able to be lucid enough that I saw through the static, and I am now able to recall the abuse and violence that I associate with doing the book-keeping. Given that the events in question were 20-odd years ago, I'm now in a position to remind myself that my circumstances have changed since then .
So now, I'm working on assuring myself that my circumstances have changed. That I was right (at the time) to make this association, but that the association is not accurate today. In the course of writing this post, I've made a plan - soon (not just yet), I'll open the accounting software, not do anything at all, and close it again.
Eventually, I'll have a new set of associations with book-keeping. That doing the books results in tender affection from my wife who recognizes how hard it was for me to do it, and other supportive responses from other supportive people. If I build up enough of those associations, then I stop being triggered by it.
I had a conversation with my father a few days ago, where he mentioned a specific fact about how he lives today - it's something that was the same as when we used to have a horrible, abusive relationship. The fact reminded me of a particular fight that we had, and of being ashamed and humiliated. Ten years ago (which was ten years after the event), that would have been enough to throw me off balance, to need to tell him about why I didn't deserve to be treated the way I was treated on that day. Today, I didn't feel that need. I was able to think "Do I want to stop this conversation, and start a conversation about this reminder, or would I prefer to leave it alone?" I was able to make a decision that was based on what I wanted, based entirely on present feelings and present reality. To me, that's a trigger that has been defused.