Can you write a list of things that show you how you're safe at that moment? Like... things about your life that have changed.

If you like/do any meditations you may want to put a reminder and instructions in it to point out what to do in case you've forgotten. You could also write down various things that are easy to do anywhere. Like focusing on the pattern of the tiles on the floor, or focus on how a piece of your clothing feels, or to observe the sounds that are occuring around you.

You could even do a "If you're somewhere where you can leave easily, go and sit and X" or tell yourself to go to a cafe and get something calming to drink, or other things that might make you feel relaxed and safe.