If you bought hard sleeper or soft sleeper on the train from Lhasa to Guangzhou, you can not get off at the intermediate station. Otherwise, the tickets will become invalid and you have to buy another new ticket to continue the trip. Therefore, you would better figure out this will before purchasing. If you’d like to stay one night in some city, you can buy two tickets respectively, such as Lhasa to the city and the city to Guangzhou.