Either you are making something new, or you are working to preserve and maintain something that was once new. One category of people builds new things so that human beings have all their human-made things, and the other category of people looks after those things once they have been built to make sure that everything keeps working as it should.
Here I am not just referring to jobs that people do for paid employment, although this principle certainly applies there as well. Construction workers, artists, and software developers belong to the former category: They create things that were not there before. Police officers, doctors, and janitors belong to the latter category: They work to protect and preserve things. But in a more general sense, the things that people do in their personal lives belong to these same two categories as well. This applies to what people do to themselves, as well: Either people are developing themselves (typically by learning new things), or they are maintaining themselves (typically through things like fitness routines and other forms of self-care). Indeed, eating and sleeping belong to the maintenance category, and thus people spend most of their lives maintaining themselves.
It is obvious, I think, that neither of these categories can exist without the other. Of course maintenance workers could not maintain anything if creators did not create those things first, but the things creators create would not be useful for very long if there weren't people who understood how to protect, preserve, and fix those things. People may debate over which category is "better" than the other; in general, one can say that being a developer is probably more glamorous than being a maintainer, but really, neither work could exist without the other.
I often think about this idea when trying to decide what I should do next with my life. The process of self-development is, without a doubt, a useful process sometimes, but if I am going to add to my list of skills and knowledge, I want to add something which I might be able to use. And the fact is that right now, I know not only everything I need to know, but even everything I think I could conceivably need to know for the foreseeable future. Obviously that could change: I might develop a new medical condition which requires me to understand how to manage that condition, or I could experience some other life event that suddenly requires me to have some specific knowledge, but I've tried to prepare myself as best I can for such exigencies, and in the last few years of my life, I really haven't had any situations where I found that I was lacking any knowledge I needed, or even knowledge I could have applied in any meaningful way. We often hear about how important it is for people to keep learning new things, but I find this process fairly useless. Most of the things that I've learned over the past few years, I've simply forgotten because of lack of use of such information and skills. You can't keep building, developing, and growing forever. At some point, you reach a state where any further development just seems pointless, superfluous, useless. If it's not serving any purpose, then why bother doing it?
On the other hand, if we don't develop, if we don't learn, if we don't have new experiences, if we don't grow, then what else are we supposed to do? What else would we do? What else could we do? Just remain as we are, unchanging, letting the days pass by, while we slowly get older and creep closer to death? We can maintain our machines. Some people still have really old cars from the early 20th century which they maintain, and you can do that if you want to, but you can't do that with a human being. Even with the best doctors and medicine in the world, a human being will eventually wear out and get old. The notion of just existing, just trying to keep everything the way it is, is an untenable idea, because no matter who you are, you will not be able to remain the way you are forever. Even if you live in the same place all your life and do the same thing every day, your body will eventually leave you. We can't just expect to preserve everything forever.
I know that some people will call this characterization sexist, but these two aspects of human behavior which I've described correspond fairly closely to "masculine" and "feminine" energies. Historically, it has generally been men who act as the builders: It has usually been men who discovered new territories, developed new machines and other kinds of technology, and did much of humanity's non-domestic work. It is this masculine drive to create, invent, and produce that motivates men to constantly learn new ideas and skills. The human male generally has an intrinsic, psychological need to feel "useful", and this need is so strong that it drives them to feel useful even when they are at play. This partially accounts for why men are usually more interested in video games than women: Video games give men the chance to feel useful by utilizing technical systems, and that is exactly what men enjoy: Learning how complex systems work, and then being able to utilize their knowledge and hard work to produce some meaningfully useful result. When they win the game, men feel that they have achieved something.
By contrast, women, of course, were generally the ones who had to look after children and a household, and this is not a role that requires "development" so much as simply a lifelong maintenance process. Although one may think that women are "creators" in the sense that it is from women that life is born, aside from the process of producing children, women are less inclined to feel the need to constantly grow and expand in some utilitarian way, but they are rather more inclined to simply relax and enjoy life while nurturing and caring for the people close to them. Where men feel an instinctual need to keep developing and building new ideas and structures, women have more of an instinct to create a home, a place where people can belong, where people can spend their lives in an environment of safety, love, and mutual care. Whereas men often enjoy video games because of the complex systems which such games contain and which need to be figured out, women are more inclined to enjoy passive forms of entertainment, typically movies and television, because these allow women to relax and live "in the moment", enjoying life rather than thinking about what they will build or develop next. Whereas men usually need to be "doing" something to enjoy life, women are more likely to be able to enjoy the act of being alive itself, even without doing anything specific to make life valuable or worthwhile.
In modern times, work has become increasingly automated by machines. It started with industrial labor, but now even much intellectual and artistic work is being done by computer software, and as a result, the role of human beings as creators, builders, and developers seems to be becoming diminished, which is part of why men feel more worthless than they have ever felt at any point in human history: Again, men have a deep, instinctual need to feel useful, and without being able to fulfill this need, men become discouraged and depressed, feeling worthless and hopeless. Even if technology were not taking that role away from men, however, basic facts of math and science suggest that all of this "growth" and "development" must eventually reach a critical point where it is no longer viable to keep building more and more. So what exactly are we supposed to do with our lives? We can't just keep developing, extending, and expanding forever, but we also just can't preserve everything and expect everything to stay the same forever. So what are we supposed to be doing with our lives, with the precious time that is given to us every day? How exactly should we be utilizing that time?
At first glance, it may seem that this kind of contradiction (in this case, between developing and maintaining) is precisely what the Hegelian dialectic was made for: Hegel saw the dialectic as a concept which takes two contradictory-but-true ideas and reconciles them into a synthesis, a unifying idea that combines the essence of these two seemingly-contradictory statements. Yet not everything can be synthesized; not all concepts can get along with each other, even theoretically. It was for this reason that modern philosophy pioneered the idea of the "reverse dialectic" or "negative dialectic", which is in essence the idea that rather than trying to somehow reconcile contradictions or blend them into a compatible union, some ideas must simply be left separate from each other, with the acknowledgment that not everything is compatible with everything else. From this point of reference, it becomes apparent that life must combine development with maintenance, but not at the same time. In order to live, you need to eat and sleep, but you cannot perform these activities at the same time, and should not attempt to do so. Rather, there is a time for one type of activity, and another time for another type of activity.
Life is a mixture of different things, and in terms of chemistry, it is a heterogeneous mixture: Not a homogeneous mixture where every component of the mixture is exactly evenly distributed throughout the entire mixture (a typical example from chemistry is salt water), but rather a chunky mixture where different parts bump up against each other, like a chocolate bar with peanuts in it. You cannot mix everything together into uniformity, nor should you attempt to do so, because some things just can't be mixed.
In a recent post, I described what I called "The ever-searching soul", the soul that is so used to finding whatever it wants right away, and so used to there always being something more to look for, that it has come to naturally and instinctively believe that it is entitled to infinity, that the infinitely-large reservoir of content available on the Internet exists just for us, and that we should be able to find whatever we want therein. This is a sort of greed, an affliction of spoiled people who believe that the world exists simply to give them whatever they want, whenever they want it, but a similar question about developing versus maintaining could be asked here: Instead of constantly wanting more content, more stimulation, more entertainment, is there value in becoming stagnant, remaining satisfied with what you have rather than trying to grow?
Again, in the end, it all comes down to balance. The human being needs to spend time looking for more ideas, more content, but it also needs to spend time in physical and mental rest. Similarly, when the human being does get busy, its activities need to be balanced out: There is a need for maintenance work that simply maintains the status quo, but there is also a need for creativity, innovation, and development. All of these go together and are a part of a consummate human being's life, but they must be done at different times, for they cannot be mixed together. Sometimes balance is about mixing things together, and sometimes it's about the opposite, keeping things separate.