The libidinal development is thus at every step influenced by anxiety. For anxiety leads to fixation to pre-genital stages and again and again to regression to them. On the other hand, anxiety and guilt and the ensuing reparative tendency add impetus to libidinal desires
Klein argues that libidinal development is a dynamic, bidirectional process perpetually shaped by anxiety and guilt, which alternately arrest progress through fixation and stimulate forward movement through reparative desire.
, Envy and Gratitude and Other Works 1946-1963, 1957thesis