"... everyone thinks his psychology is the measure of all things..."

Psychology

“To relieve the isolation and confusion of modern man,

 to enable him to find his place in the great stream of life,

to help him gain a wholeness         

                  which may knowingly and deliberately

    reunite his luminous conscious side

    with his dark unconscious side

                                                                                              -- Jacobi

Just as the body has its own stages of development, the mind also has successive psychic stages and achievements that we attain via the vehicle of effort, not (necessarily) time. 

There is a universally inherited urge among all of us towards the same attainment – Individuation. 

And for all of the things you can do to improve your life - nothing else can give you as much return on your investment as consciousness can. 

We actually spend more time in the unconscious part of the mind than we think, and if I came to write this paper with one goal – it was to emphasize above all things the importance of developing consciousness, in order to facilitate the Individuation process. 

Simply put, there are 2 major advancements in the adult phase of life to achieve Individuation. 

Just as a muscle either grows or atrophies pending usage, consciousness too must be exercised in order to become stronger, otherwise it too atrophies[2] - into unconsciousness. 

Consciousness is the workshop where the manufacture of creation exists - and the more consciousness you have - the more potential you have to create.

Psychology strives primarily to understand the hidden aspect of each individual and relate it to the manifest aspect.  The "externam" frequently takes the form of behaviour, communication and the projected image that one wants to share with others through clothing, general appearance and other mannerisms.  The "internal" is the underlying processes of the behaviour, and the metacommunication of communication.  Simply stated, psychology strives for congruence between the conscious and the unconscious.  JViJP 72

Caveat Emptor:   It is a remarkable fact, which we come across again and again, that absolutely everybody, even the most unqualified layman, thinks he knows all about psychology as though the psyche were something that enjoyed the most universal understanding. 

In Jung's own words:  

    In psychology one possesses nothing unless one has experienced it in reality. Hence a purely intellectual insight is not enough, because one knows only the words and not the substance of the thing from inside.