微笑只是你给我的外衣
[wēi xiào zhĭ shì nĭ jĭ wŏ de wài yī]
The literal translation is 'A smile is just the cloak you gave me.' It implies that the person is putting up a brave face and smiling only as an external appearance to cover inner emotions like sadness or vulnerability, usually due to another person's influence or expectation.