As there must be moderation in other things, so there must be moderation in self-criticism. Perpetual contemplation of our own actions produces a morbid consciousness, quite unlike that normal consciousness accompanying right actions spontaneously done; and from a state of unstable equilibrium long maintained by effort, there is apt to be a fall towards stable equilibrium, in which the primitive nature reasserts itself. Retrogression rather than progression may hence result.
"The Principles of Ethics" by Herbert Spencer, (Ch. 10), 1897.