But, someone once gave me something I can use even in the crisis moments: Zen breathing techniques! For me, this has worked pretty well.
I am no master of this at all, but I learned enough to know that when I become afraid, I want to hold my breath, and this natural urge compounds my troubles. Now, I have learned to breathe from my diaphragm. This is sometimes called "belly breathing". The effect is a good one, because when you can control your breath, you can act against both your Fear and Anxiety as well as the physical responses they tend to create.
Belly breathing is a method you learn that requires you to breathe much more deeply---instead of drawing breath from your chest alone. For me, the technique begins with an exhale: I place a hand on my belly above my waist to feel the muscles contract. When I can exhale no further, I draw in a breath, slowly and deliberately, feeling the muscles in my belly act to draw in my breath. This makes me want to relax, and so I allow myself to feel the relaxation. Then, I do it again. For me, it can take five or six breaths to calm me down, or several more than that. I keep my posture straight when I do this, as it assists the action. I can do this sitting, lying down or standing (although I don't usually like to do it standing because I don't always trust that I won't fall over...).