有时快乐无边无际有时心底充满恐惧
[yŏu shí kuài lè wú biān wú jì yŏu shí xīn dĭ chōng măn kŏng jù]
This indicates that emotions, such as happiness and fear, are not limited but can vary immensely from feeling boundlessly happy at one time to being overwhelmed by fear deep down inside the next. It highlights the spectrum of human emotions.