The human self (is) not simply a finished product, a kind of entity, but a developing process. A self is not simply something I am but something I must become. To be sure, there is also a sense in which the self must have a kind of substantial reality, for there must be something that is undergoing the process of becoming. But the substantial reality of the self includes potentialities, and thus selfhood is a process in which a person must try to “become what one already is.” This unfinished self gives shape to itself through its choices; every decision I make is also a decision about what kind of person I want to be.
C. Stephen Evans, Introduction: Kierkegaard’s life and works