One of the things I have noticed that has meant so much to me is finding myself less concerned by what other people think. High school (middle school...) makes us believe that all we know and will ever be is encapsulated in a few short years. We spend way too much time caring about what other kids say about us (when they don't know anything—at least not any more than we do). I have a better sense of self now. I know that if I've worked hard, I've done a good job and no one needs to tell me (though it's always nice to hear it). I also know that I make mistakes, but can forgive myself more easily and laugh at myself more easily. It's not always a perfect system for me: sometimes there are things I know I care about more than the time they are worth worrying about, but it's so much easier now.
Of course, the problems and worries we face when we are older become more serious: fear of losing a job, worrying about the health of children and parents, losing friends to illness or accidents, etc. These are things that happen to young people, too, but the frequency increases as we get older. We worry more about things we didn't have to when we were younger: like politics and taxes.
However, with maturity comes a certain peace, if you're lucky. Maybe it is something we have to spend time working on...consciously. I am more apt to stop and help a stranger (hold a door, carry something to someone's car); I love to compliment people if I feel honest about doing it. (Drives my daughter crazy because she says it's embarrassing, but that's her age.) I know how nice it is to hear nice things from others, so I pass it on. And there is a sense of giving back. When you're more comfortable financially, mentally and emotionally, it's easier (if you're lucky...) to appreciate all that you have and to give back to those who are less fortunate. And I've found it has nothing to do with making me feel important. If someone feels good because I've been able to help in some way, I feel like I've been given a gift. Now it still bothers me if I try to be nice and someone blows me off; I'm still human. Having to look in the mirror is not as easy: those little lines and extra pounds can be a bother, BUT I SEE MYSELF AS A KID AT HEART, and it's easier to age more gracefully that way. Years do not an old person make: some young people are old their entire life.
But many things become less worrisome as we "grow up." And there should be some good that comes with no longer being 25!
As we grow older, I am sure that is what you are referring to, we certainly have to develop physically, emotionally, and psychologically. Sometimes, we even have to develop as social creatures by learning to understand the differences of others as a normal part of being a human being.
Erick Erickson is probably one of the best social scientists to study, as his epigenetic stages of development clearly mark how we change, what is expected at each stage of development, and what could happen when we either bypass or do not fulfill the stage in its entirety.
Putting myself forward as an example, in my 30's, I experienced several life-changing events that often go hand in hand with my age group: I finished Grad school, entered a couple of more challenging jobs, became the mother of a teenager, and saw myself taking care of my parents, who had to re-invent their careers due to the economy. I also faced the death of my grandmother, and the early death of my significant other's brother, who died of cancer too early in life.
All these things may happen at any age, but when you look into the specific age group of which I am talking about, you realize that the events that have taken place are almost expected when you have complied with those "life stages" that come with our age.
I would expect a fairly large divergence of answers in response to the question of what changes we face as we age.
Some people "come out of their shell" and become more social in ways that may last a lifetime. Others who were social and engaged in their youth may decide that family is enough and withdraw from "active" social life.
What happens for you will depend on your personality as well as the experiences you have as you age.
Some changes I can share from my own experience:
I learned to cook after college (not especially well) and have made my own dinner five or six nights a week since then. I'm starting to get tired of cooking. I hadn't expected that.
Running is my favorite form of exercise and I've been running since I was 20 or so. Over a decade later, my knees are starting to hurt. I run anyway.
As one gets older, one realizes how much they don't know! When you're younger, you think you know everything. But as times goes on, that all changes. This could affect your interests, as you may now be interested in learning about topics you thought you knew everything about. Furthermore, your interests will change based upon experiences. If you never were sick a day in your life, but you suddenly develop an ailment or disease, you may now become intensely interested in health and wellness. Likewise, if your significant other has interests other than yours, you may want to learn about these interests, whether it be a certain sport or a certain hobby. Your children would also play a similar role. People and experiences will impact your interests as you get older.
Aside from the most obvious physical changes, such as puberty, we usually go through some type of philosophical and/or spiritual awakening. This is generally the realization that the nature of life is not what we thought it was as a young child. We begin to question the nature of our existence on the deepest level. This can lead to a deeper understanding of life, or, if we are unable to come to grips with it, a sense of frustration that may lead to other problems.
All of the previous posts offer excellent answers. As you age, you also mature, and your likes and dislikes change, too. I find myself wondering about the unusual fads and distractions that young people find so tempting, and most of them seem senseless to me. But I remember all the odd things I did as a youngster, and I try to be tolerant of today's changing ways.
As I get older, I am finding I place a much higher value on people and experiences and much less emphasis on "things." I have never liked to shop, but absolutely detest that process now. I would much prefer to spend my time and money sharing a special activity with people I treasure instead of acquiring more clothes or stuff I have to clean and care for.
One of the major things that happens to us is that we become less self-centered. We tend to focus less on what we think we would enjoy. Instead, we try to think about what is best for other people (such as those in our families). This is one of the major things that changes about us as we grow up.