The Concept of Anxiety
All of Kierkegaard's books have either a preface, dedication, or prayer at the beginning. This book includes a lengthy introduction. "The Concept of Anxiety" was published on exactly the same date as "Prefaces", June 17, 1844. Both books deal with Hegel’s idea of mediation. Mediation is a common thread throughout Kierkegaard’s works. His work up to this point was to show that faith was being mediated by knowledge. Here he takes up the questions of sin and guilt.
Knight of faith
If I am anxious about a past misfortune, then this is not because it is in the past but because it may be repeated, i.e., become future. If I am anxious because of a past offense, it is because I have not placed it in an essential relation to myself as past and have in some deceitful way prevented it from being past. If indeed it is actually past, then I cannot be anxious but only repentant. If I do not repent, I have allowed myself to make my relation to the offense dialectical, and by this the offense itself has become a possibility, and not something past. If I am anxious about the punishment, it is only because this has been placed in a dialectical relation to the offense (otherwise I suffer my punishment), and then I am anxious for the possible for the future. Thus we have returned to where we were in Chapter I. Anxiety is the psychological state that precedes sin. It approaches sin as closely as possible, as anxiously as possible, but without explaining sin, which breaks forth only in the qualitative leap. Søren Kierkegaard, "The Concept of Anxiety", Nichol p. 91-92