Part Two states that "despair is sin," and the appendix to this "Christian psychological exposition for Upbuilding and Awakening" discusses forms of that sin.  
Part One defines the titular entity as "despair," which is "a sickness of the spirit, of the self, and accordingly can take three forms: in despair not to be conscious of having a self, in despair not to will to be oneself, in despair to will to be oneself."  Part Two states that "despair is sin," and the appendix to this "Christian psychological exposition for Upbuilding and Awakening" discusses forms of that sin.  FTP, identify this work, published in 1849 under the pseudonym Anti-Climacus, which begins with a discussion of Chapter 11 of John and the story of Lazarus, a work of S?ren Kierkegaard.
Part One defines the titular entity as "despair," which is "a sickness of the spirit, of the self, and accordingly can take three forms: in despair not to be conscious of having a self, in despair not to will to be oneself, in despair to will to be oneself."  
The Sickness unto Death