What are the motifs in Tropic of Cancer by Henry Miller?

Suffering is a theme in the book. The artist suffers, the poet suffers and the writer suffers. This culminates in Henry's winter spent in Dijon where he feels complete dejection. Up until this time he felt hunger, fear of losing his job, worry about where his next meal will come from, anger and disgust with those around him, frustrations in love affairs, but these little and common sufferings are nothing compared to Dijon. The suffering must be life-changing in order to ignite the transformation from being dead like the moon to being a writer, artist or poet.