Anyone experienced culture shock before?

One of my friends experienced culture shock.Well,the term culture shock was introduced for the first time in 1958 to describe the amxiety produced when a person moves to a completely new environment.And now we can describe culture shock as the physical and emotional discomfort a person suffers when coming to live in a place different from the place of origin.Different people have different views on culture shock.Some people will feel sad and miss home much.They seldom talk with others and get hypochondria finally.On the contrary,some people are very optimistic and make many friends whenever they get to a new place.They just have a short culture shock.What do you think of culture shock?Have you experienced before or your friends?