Ruben's celebrating when something goes his way is part of his strategy, and it definitely works for him. It's not really meant to make his opponents lose their confidence or their concentration, though it does help. Ruben's prowess at VGC is greatly affected by his mood. He needs to think (no, he needs to know) that he's going to win to actually do it. He celebrates every little thing to boost his morale, it's not meant to be arrogant.