Tough thing to do –
Some tips –
-visualize the video camera up in the sky recording every movement, makes it easier to smile and calm down.
-find a mantra – (Ein Od Milvado, I can get through this, kol ma d’avid rachmana l’tav avid, it’s all good – a calming song, a jingle that makes you laugh)
-concentrate on something else that’s nonconfrontational – for example, try to concentrate on perfect penmanship, perfect diction, perfect posture – just something to make you focus on something else till your emotions cool.
Good luck – remember it is the trying that gets you credit not the success!