Once I identify something as triggering I try to do the things Andy talks about - once we can talk about these problems they begin to lose their power to hurt us.
But if I am in a situation and find that I am getting badly triggered, there are several things I find I can do. One is just to remove myself from the situation. If I am watching a film, for example, that I find personally distressing and triggering, I don't have to sit there and suffer through it. Another thing that works for me is to tell myself that the time of danger is long since past and that I cannot be hurt now as an adult like I was when I was a boy.
We can also try to prepare ourselves and understand why we get triggered, so when the situation comes up we will at least not fall into a restrained panic. I am thinking here of things like being touched or complimented. I used to hate both, and that set me up for a lot of trouble since in both social and professional settings you get handshakes, pats on the back, and so on.
Perhaps a crucial point in all this is to try to stay present, in the here and now. It's in the old memories of the past that we are most likely to get ambushed. That said, I think we will still get taken by surprise from time to time, and when that happens it's important that we not blame ourselves and feel defeated. We need to just get up again and keep going.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)