I experience severe anxiety and PSTD symptoms, frequently. One of the things that has helped me to remain focused and centered is to practice "The Now."
Staying in "The Now" is when we deliberately and actively recognize our immediate surroundings using every sensory organ. An example might be as follows:
I can feel where my fingertips connect to the keys on my keyboard
The keys are smooth
I can smell the aroma of coffee and the trash that needs to go out
I can hear crickets chirping and a breeze blowing
I can feel the breeze on my face - it is neither cool nor warm
I can feel where my bare feet are touching rocks
And, so on. It is a blow-by-blow recognition and inventory of everything that we can experience, right now. This brings us back to the present. And, say it out loud if you need to.