Maturity is, as the psychic development of the individual, a short repetition of the course of development of the race.

Maturity is knowing where one's craziness lies, trying to warn other of the fact and striving to keep oneself under control.
Maturity is bored. Few realize how bored out of their minds they are by what they get from the news media.

Maturity is a process characterized by a series of energy displacements or object substitutions whereby the source and aim of the instinct (i.e. Oral pleasure) remain the same when the energy is displaced (into smoking, kissing, etc.).
The part of the human brain responsible for making 'rational decisions' doesn't fully mature until we're about 25 years old.
When does a Cub Scout become a Boy Scout?When he eats his first Brownie
Maturity is achieving a state where one no longer registers surprise or disillusionment or doubt over evidence that depravity exist, or of the kinds of things humans are capable of inflicting in the way of gruesome, hands-on cruelties upon other humans.
At what age does it change from 'pretending' to 'lying'?
Bees are born fully grown
Female Greenland sharks reach sexual maturity at age 150
