Smile doesn't have national boundaries.It is the bridge of communication between heart to heart.If in a foreign country,when you see the smile on a stranger's face,it can make you feel warm ,although in this kind of season.
maybe we can't communicate with the foreigners well in english.
But don't be stingy about your smile ,any time ,any place ,to anyone.it can be the most beautiful of your smile with sincerity.
ANd smile is also a kind of sure to others' respect.
我有点事要出门 不好意思了