抬头微笑低头哭泣
[tái tóu wēi xiào dī tóu kū qì]
'Tai Tou Wei Xiao Di Tou Qi Tu' translates to 'Raising head with a smile, lowering head with tears.' It indicates that this person can only be truly joyful and show sadness when they are alone; in the presence of others, they have to keep up appearances and pretend they're happy.