I remember this day too. I'm sorry for your difficulty -and everyone.
There is a young girl at DD's school who's birthday is 9/11 and DD said that she cries every year. They're very young kids but still full of empathy and learning about it all.
Anyway...your topic of triggers spoke to me because I've been working on them, too...I want more of my life back and the triggers are holding me down, so I've been searching for ways to cope.
One coping mechanism that I can share from a counselor takes time but is worth it. She told me to change my thinking when "trigger thoughts" enter my head and to start that is to be aware that it's happening. That the thoughts are happening.
For me, the triggers cause panic and that's something I'm learning to understand more of in order to fend it off.
She also said that being aware of surroundings and the present are helpful reminders that we are "ok". She would remind me to tell myself that I was ok and even things like the date and time or a trivial to do list help make the day more routine and can combat a trigger. Then there is the activity on the list and today to think about instead and later, at night, an accomplishment for the day that was today and not the past. It's not to discount the past, but to try to not make it so huge in our minds.
A person is a person, no matter how small. -Dr. Suess
Perserverance and spirit have done wonders in all ages.