A quote that made a difference for me, addressing the paralyzing issue of "what if I'm wrong? what if I make a mistake in front of all these people?":

though it cannot hope to be useful or informative on all matters, it does at least make the reassuring claim, that where it is inaccurate it is at least definitively inaccurate. - Douglas Adams

If I'm wrong when speaking to a group, then by gum I'll strive to be definitively wrong.