人潮拥挤他心难入
[rén cháo yōng jĭ tā xīn nán rù]
This roughly translates to 'In crowded places where there are so many people, it's hard to enter his/her heart'. The phrase expresses feelings such as jealousy, inferiority complex or frustration of having difficulty approaching or getting intimate with someone else. Also, it may refer to being excluded and lonely even amidst a bustling society.