Every short holiday, the circle of friends is screened by photos of various trips: not only the magnificent mountains and rivers of the American emperor, the prosperity of the metropolis, the blue sea, food and shopping, but also the kind of happy group photo with the words "Thank you for xxx's company/leadership, thank you for meeting these little friends, it's good to have you". This time is often the saddest-why does everyone look so lively and colorful?