There's this really easy breathing technique. It combines natural breathing and a special word, like calm....
When you want to reorient, just remember your breath!
First, tune in to how you're breathing. Notice whether your breathing is shallow or fast. Then take one deep breath, and let it out nice and slowly.
Next, allow yourself to begin breathing naturally. With every exhalation, say the word "calm" under your breath. Really drag that word out; make the out breath last a nice long time. C-a-a-a-a-a-a-a-l-l-l-l-l-l-m-m-m-m-m-m-m-m.
Naturally inhale, then a nice long exhale with the word c-a-a-a-a-a-a-a-l-l-l-l-l-l-m-m-m-m-m-m-m-m.
You can also pick out a different word, one that suits the situation best.
Do this for about 10 breaths and notice what happens.