伤心时不要听慢歌
[shāng xīn shí bù yào tīng màn gē]
This means 'Don't listen to slow songs when you're sad'. It reflects a person who is in pain and believes slow melodies might deepen his/her sorrow. The user may be expressing that they should not indulge in their sadness but instead try to cheer up or keep emotions under control.