all good advice.

My one tip would be that 2 minutes before you go on, go somewhere like a toilet cubicle where you can sing your favourite song as loud as you can. In fact it doesn't even have to be your favourite song- something ridiculous like You Give Love A Bad Name by Bon Jovi or Don't Stop Me Now by Queen will often do the trick better. Singing the stupidest song you can think of, really loud, will cheer you up and remind you that it is impossible to truly make a fool of yourself.

Similarly note, giving yourself a big round of applause, doing some whooping and cheering works well. that's something a drama teacher once showed me, before a student play.