There are many ideas about how we grow up, and this is my take on the process from my own observations.
Psychology is trying to come to grips with how we grow from child to adult, and the processes involved. Writers from Noam Chomsky to Ann Ree Colton have all contributed their ideas based upon their research.
I have observed that a personality seems to develop its aspects with a decade roughly apportioned to each stage within it, though there is overlap between them. Also, development of each stage doesn't stop, but the large core of it seems to be within its decade. Note that these are largely separate from our connection to our inner wisdom, which will define how effective we are at each of the stages.
From the moment a child we are born, we are trying to take charge of our physical environment.
We are trying to manipulate the things around us, and expressing our frustration when our efforts fail by crying, hoping someone else will do it for us. We grow from the tiny to something most of the way to our final height and form, with the major growth in the first few years. We may get upset, but we don't identify with it, as it is just a tool to get things done for us.
In the pre-teens and teen years, we identify with our emotions.
This stage is about how we experience emotions and gradually learn to take some sort of control over them. To a large extent, it is a time of owning emotions and being them, as an experience in itself. This is why how we feel is very important to us as teens, especially since we do not have much more to work with. We learn some reasoning, but our anchor is our emotions. It is the reality from which we reason.
Having achieved some control of our emotions, by the twenties, we are ready to develop our mental faculties.
Compared to emotions, the mental level seems to offer a whole lot of possibilities. We are ready to explore ideologies and what they have to offer. It seems as if there is nothing that is not possible.
By the mid-twenties, there begins the realisation that while there may be an infinite number of possibilities, we are not capable of achieving them all. The earlier stage was about stretching our mental faculties as if there were no boundaries, but that is now replaced by the practical concerns and limitations of physical life and our responsibilities.
Near the end of the twenties comes the Saturn return, which is about us making choices about our future and letting go of those things and attitudes that will impede us achieving what we envision.
Having the three parts of the personality built up as much as they are going to be, it is now time we bring them together.
Of course, in earlier stages, we will have been integrating the prior stages to some extent, but now we have the capacity to start consciously and willfully directing our emotional and physical bodies in a concerted way. It is a time of integrating our bodies into an effective whole. We may have jobs that require all of our being, pulling together all of our resources to achieve particular ends. We may improve our people skills, enabling us to direct others towards the same goals.
With an integrated personality, time is ready to embark upon the real purpose of our life.
The forties are a time when we know what we are capable of, and so we have a fair idea of what is the best work we can be doing. It is a time of making our stamp on the world, having a strong sense of mission or destiny. Through learning enough about ourselves and others, we can work with some wisdom, becoming more effective.
Normally reaching the twenties carries an expectation that we have some level of maturity, but there is still much to learn.
In our twenties we can often react and act on impulse. Without a developed and stable mental body, it is hard to effectively direct our efforts. There are still too many non-cooperating moving parts within our personalities. Maturity is not just about experience. It is in having enough anchor points in our sense of self to keep emotional and mental balance when confronted with life's challenges.
This means that in some circumstances we can be mature, and act with some certainty and balance, whereas at other times we can overreact, be emotional or otherwise act immaturely. Those parts of us that did not completely develop in earlier stages will undermine our efforts, but we can make choices to be better people, and consciously work on ourselves.
Note that maturity is not an indicator of wisdom, self-awareness or level of empathy, but just how certain we are of who we are and our responsibilities, which might just be clouded by delusion. However, we would normally expect to gain some of these extra qualities as we go through life, but that is not guaranteed.