Everyone in Korea and many Koreans living all over the world eat tteokguk, 떡국, on New Year's Day because it is believed to bring you good luck for the year. Also, in Korea, you can't become one year older until you have a bowl of tteokguk. A common greeting around New Year's Day for Koreans is "Have you eaten tteokguk yet?" So, have you had your tteokguk yet?
If you are not familiar with theokguk, it is a hot beef broth soup with thinly sliced rice cake (tteok) garnished with marinated beef, thinly sliced fried egg, and dried seaweed (gim). People also frequently add dumplings (mandu) or scallions (pa). It is definitely a comfort food perfect for a cold, winter day.