总有一个孤独不离不弃
[zŏng yŏu yī gè gū dú bù lí bù qì]
The phrase translates directly as 'there will always be a loneliness that does not leave nor abandon'. It's often selected by introverted users as an expression of deep feelings about constant but unwanted presence of loneliness in one's life, which might seem inseparable.