What's to be nervous about? I imagine you would only feel nervous you if doubt yourself or your abilities! lol 
Liam, I will have to debate this with you, ok.
Being nervous, isn't necessarily about doubting your abilities, I know that I can perform Heian Nidan (ish) I did so today, nerves arise from the feeling that you want to perform everything the very best you can, for example, for the 32 seconds of kata for Heian Nidan, you want to give everything you have, and a bit more.
In my opinion, questioning your ability, is good, it pushes you to strive to do better. Ask yourself this, if you will.
Why continue to practice, say from one month ago, when we got up in front of the class to perform our katas? I think we all did them reasonably, so is it doubt about our ability that make us practice, or, it is the desire to do our best?

EDIT: Fixed quote 2nd edit: (fiddler

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