For many years I always looked up, when walking home from the pub, to check whether it was a full moon or not. If it was, I took great care, after arriving home, not to look out of the window because ('as everyone knows'!) it's unlucky to look at the full moon through glass.
It was only when I mentioned this to my girlfriend that it was pointed out to me that, since I always wear my glasses, I would have already looked at the moon through glass when checking to see its phase ;-)