Sorry your feeling anxious at work :( I know all too well what that is like! This week has been hard for me too! I work in a medical office and so I am with patients a lot and in the center of attention. If I find myself having a hard time, I worry that the patients will notice. NEVER once has anyone said anything. If I am really bad off, I excuse myself to the restroom and look closely at myself in the mirror and say "your okay, its just anxiety, you will be just fine" I feel silly doing it, but it works for me. I also practice some deep breathing. When I clean the patient tables after they leave, I use that as an opportunity to take a few deep breathes.
Whatever your situation, try to find a way to sneak in a few deep breathes, positive internal dialogue is important and if you can't dismiss yourself at the moment, try to really interact with your customers as a way to distract yourself from whatever it may be.
Hopefully you will get relief soon.