Though this is a topic I can write endlessly on, I choose to summarize this as briefly as I can.
Maturity is something like humility. The moment people think they have it, they self-defeat themselves. – Marcus Hades.
Maturity is not a norm, but has to be judged from both angles – the one viewpoint is of the person who is judging, and the other is of who is the executioner of the judged act, speech or thought process. I believe most mortals have an equal amount of strengths and weaknesses. Where the difference lies is what one is using to make a choice, or respond to an event – the strengths or the weaknesses. Ideally, I believe that a person who uses his/her strengths more, than he allows his/her weaknesses to dominate a resolve or opinion towards shaping his own destiny is a mature individual. As age happens to anyone, the problems and struggles in life increase and the ability to keep the focus in these situations, and not fold, is maturity.
Social interactions are often misjudged by people in anticipating maturity levels in the opposite people, as most people mask appearance, speech and behavior to hide inner strengths/weaknesses (mostly weaknesses) so as to present an uncomplicated version of oneself to the world or to portray oneself as he/she wants others to perceive.
Ways to judge if a person is mature are many, but taken only by the ones who are actually ‘mature’. These include coherent thinking and logical explanation in solving a problem, and the art of reasoning while speaking, discussing or debating. The actually immature ones will simply dismiss the opposite person's thought pattern and not understand what drives the other person. That explains quite a lot about why a generation gap exists amongst some parents and their children, and why are some parents and children so understanding and amicable.
In the mortal flow of thought processes, maturity mostly is taken to be a matter of age and experiences one has gone through. Also, the ‘mature’ person may come to think of anyone as ‘immature’, who thinks differently or does not agree to the mature person’s line of thought. Anyone who agrees to ones thought pattern is presumed as ‘mature’. I haven’t come across anyone who would say, “Hey, you think just like me. How immature we are!”
Maturity according to me is not a matter of age, but a matter of how we choose to develop our thoughts and responses flowing through life. It depends on responses and experiences which in turn are based on our value and belief systems. It is again not necessary that the responses may be constantly ‘mature’ throughout one’s life. I believe the toughest challenge is in finding the balance between the IQ and the EQ (emotional quotient) and responding in a manner which is the most feasible or reasonable (not necessarily only practically).
Maturity is not to be judged by external introspection only. It takes months or sometimes years to gauge if a person is more bent on the mature or immature side. Most importantly, the levels of interaction to gauge whether a person is mature or not, have to be personal as well. A newly found friend, a distant relative or a friendly co-worker for example can never get onto those levels. Only a determination of one's entire belief and value system (and actions based on them) can be a determinant in gauging whether a person is mature or not.
Maturity is not something which has to be persistent, but solely dependent on a set of actions and that too with a particular set of people, in a particular situation. Eg. A person may be immature in behavior when it comes to friends, acquaintances or coworkers but may be a very mature individual with family and vice-versa. Also, a person may be mature when it comes to making life’s tough decisions and always find the best possible way out of an adversity, but may be confused in small everyday decision making and may be clumsy in them. A person may also portray a very immature kind of behavioral pattern to whoever he/she interacts with, as a choice, but must be a mature person in his/her thought processes.
A few words said; I believe that a person may not be able to take 'mature' decisions at all junctures in life – because we all lose focus at different points in life when choices have to be made. Such choices are often hard. The ones who make such hard choices, who know when to take a calculated risk, who are empathetic, who think for themselves and are not influenced entirely by society, who are willing to face adversities in the pursuit of something worthy and be willing to sacrifice themselves for the ones they love or for the greater good, are mature according to me. Which situations govern thoughts at which time in life, are solely left to the person executing such thought or action.