Man is Growth

We are what we eat; we are what we think.

Earl Nightingale
Widely respected as the father of modern day personal development.
Called the ideas in As A Man Thinketh the "strangest secret" – the secret being that "we become what we think about."

From As A Man Thinketh:
"Man is a growth by law, and not a creation by artifice, and
cause and effect is as absolute and undeviating in the hidden realm
of thought as in the world of visible and material things. A noble
and Godlike character is not a thing of favor or chance, but is the
natural result of continued effort in right thinking, the effect of
long-cherished association with Godlike thoughts. An ignoble and
bestial character, by the same process, is the result of the continued
harboring of groveling thoughts."