For me it depends on what the trigger is, and where I am. If I'm around other people I will NOT do anything that would visibly look like I'm distressed. So I might breathe slowly and shallowly. I might grip my fist and focus on the feeling of that. Or I might fidget with an object near me, and focus on it.

One of my triggers is feeling like I'm trapped somewhere (and yet, I am not claustrophobic!). I'm in a small, very isolated town which reminds me of my hometown. This makes me feel incredibly trapped and is a constant trigger whenever it hits my thoughts. I tend to remind myself in my thoughts that it is NOT going to hurt me - I'm not with my family, I'm in fact an entire day away from them. I remind myself that I chose to be there for work, that I love my job, that I am earning good money and can go on a vacation, etc. I talk myself down from the trigger.