黑衣的寂寞你不懂
[hēi yī de jì mò nĭ bù dŏng]
The literal translation is 'You don't understand the loneliness of wearing black.' Black clothes are often associated with a quiet or lonely figure, so it means people around you can't truly comprehend what kind of solitude one may feel internally when putting on an indifferent face. This conveys a feeling of being misunderstood.