Our many different cultures notwithstanding, there's something about the holidays that makes the planet communal. Even nations that do not celebrate Christmas can't help but be caught up in the collective spirit of their neighbors, as twinkling lights dot the landscape and carols fill the air. It's an inspiring time of the year.
Your brain sends out vibrations all the time, and your thoughts affect your life and other people's. They pick up these thoughts and get changed by them. That's why, say, a pacifist gets caught up in a riot situation. It's a field of vibrations - you can 'feel' someone else's thoughts when close to them.