Don't stress too much because you might get lucky and just be waved through.  I am an American Citizen and sometimes still get shit at the border. Then sometimes I am waved through easily. It is just the luck of the draw. If they do stop you stay polite (obviously) and you will be fine. Even if they take you into a little room it probably doesn't mean anything. People I know have been pulled aside and detained for a short while and then let in.