At stage two it is disproportionately important to get a good night's sleep and a decent breakfast in the morning too!
It's a hard day, there's little doubt about that, so try to socialise and relax with the other candidates, they will help to put you at ease. In fact they may even recognise you're name from this site (I was "outed" by a fellow PPRuNer!).
I had a fun day when I did my stage two, came out thoroughly tired but happy enough. That should be your aim. That way you will perform to the best of your ability!
Phil