Adulthood is the realization that sometimes an abstract principle is right and good for its own sake, that even if it hurts you today, even if it hurts others, being honest is still the right thing to do. In the same way that the adolescent realizes there’s more to the world than the child’s pleasure or pain, the adult realizes that there’s more to the world than the adolescent’s constant bargaining for validation, approval, and satisfaction. Becoming an adult is therefore developing the ability to do what is right for the simple reason that it is right.

Adulthood essentially means making the right choices based on true love.

Adulthood is the ability to be totally bored and remain standing.

Adulthood is not just gauged by years survived. An adult is able to act independently, to resist manipulation, to make his own decisions. And to take the consequences.

One might define adulthood as the age at which a person learns that he must die ...and accepts his sentence undismayed.

The hard reality is that adulthood is not necessarily an age. It's more a skill.

Childhood is that time in which we never question the fact that every adult act is not only an autonomous occurrence in the universe, but that it is also filled, packed, overflowing with meaning, whether that meaning works for ill or good, whether the ill or good is or is not comprehended.
Adulthood is that time in which we see that all human actions follow forms, whether well or badly, and it is the perseverance of the forms that is, whether for better or worse, their meaning.
Various cultures make the transition at various ages, which transition period lasts for varying lengths of time, one accomplishing it in a week with careful dances, ancient prayers, and isolate and specified rituals; another, letting it take its own course, offering no help for it, and allowing it to run on frequently for years. But at the center of the changeover there is a period—whether it be a moment’s vision or a year-long suspicion—where the maturing youth sees all adult behavior as merely formal and totally meaningless.

The allure of adulthood includes being allowed to drink alcohol, enter a club or bar, browse any website and other pleasures. The period of abstinence is designed for us to later abhor these things or love them in moderation. Growing up really is a journey towards the light because childhood is a sort of tyranny.

We achieve some measure of adulthood when we recognize our parents as they really were, without sentimentalizing or mythologizing, but also without blaming them unfairly for our imperfections. Maturity entails a readiness, painful and wrenching though it may be, to look squarely into the long dark places, into the fearsome shadows. In this act of ancestral remembrance and acceptance may be found a light by which to see our children safely home.

Surely the human race is at last reaching the stage of adulthood — that adulthood of character which does not depend upon physical age at all — so that it is deliberately embracing responsibility for its own development and government, and trying to face up to the causes of its failures?

Adolescents are simply those people who haven't as yet chosen between childhood and adulthood. For as long as anyone tries to hold on to the advantages of childhood—the freedom from responsibility, principally—while seeking to lay claim to the best parts of adulthood, such as independence, he is an adolescent. [...] Eventually most people choose to be adults, or are forced into it. A very few retreat into childhood and never leave it again. A large number remain adolescents for life.

We achieve some measure of adulthood when we recognize our parents as they really were, without sentimentalizing or mythologyzing, but also without blaming them unfairly for our imperfections.

Adulthood feels like walking around in the desert with a bag over your head, being bumped into by people who rob you as they bore you.

The modern Millennial, for the most part, views adulthood as a series of actions, as opposed to a state of being. Adulting therefore becomes a verb.