Are you all tense? Try deep breathing. Then watch your shoulders automatically relax. May take a few tries, but it seems to slow down my heart rate a bit. Maybe not my mind...

Do you take meds for your anxiety? Warm milk and honey works! Seriously!

I'm always anxiety ridden. These tricks might not last long, but at least it gives a few seconds/minutes of relief.

Sometimes, though, I'll try so hard to concentrate, that it will makes it worse.

These are little reliefs, so don't expect miracles. But keep deep breathing when you can remember. That actually stays with you the more you practice.