收拾深浅不一的孤单

This translates literally to 'organizing solitude of varying depths'. It's a metaphorical statement that can mean one is sorting out various forms of loneliness within their own mind, perhaps trying to understand or cope with complex emotions of seclusion or sadness. Each person can feel loneliness in different levels in his inner mind, like shallow, moderate, intense, so the user here may be expressing that he is processing all kinds of loneliness.