Our brain's ability to develop new patterns and provide us with learning is the same ability that gets us stuck in the habits we do not want. We tend to develop rigid behaviour as we get older and this is the cause of many problems associated with age. This negative change can be reinforced by your everyday choices if you don't pay attention to it coming, or it can be transformed and used for the purposes of adding quality to your life.
Our vitality and well being is dependent on our brain chemistry. It is affected by our interaction with environment, nutrition, social relationships, quality and amount of movement etc. When we develop rigid habits that we repeat day after day in the simplest of actions, our life enters auto pilot and as a matter of fact we lose our control over it. I don't want to say that developing habits is entirely a bad thing - it is unavoidable for any sort of serious achievement and an inherent part of learning, but there are a lot of them that sneak into our life without us even noticing and that we don't need. The less variation we provide our brain with, the more dull its perception of the world becomes. We all have seen people who resemble zombies, day by day doing the same actions without paying any attention to them. Getting into the comfort of following the furrow you make for yourself day after day is a very common path to chose, but as there is not much thinking needed, with time our brain loses any need to evolve. This results in the behavior we usually associate with aging, which is not really a result of the aging itself, but rather of the choices you make on how to approach your life on a daily basis.
The same rules can be applied to movement as they can be to life in general - repeating the same thing over and over again without any variation leads to injuries and inbalances. I don't want to say that there is no need for repetition - I want to say that you have to pay attention to what you do and spot the habits that might lead to damage. In fact, no movement that you do is the same. Each time you are trying to repeat a pattern, there will never be two motions that are identical. This is important to understand if you want to develop healthy and functional movement - if you don't pay attention to what you do, don't analyse it and correct it in the process, chances are you are going to develop either rigid and robotic patterns or noisy and unstable ones. Which in both cases means lack of quality and real understanding.
Movement it is the most important source of nourishment for your brain (Ratey JJ, Loehr JE 2011), moving in the same manner over and over again doesn't provide your brain enough stimuli for enriched development, so to save energy it stops building new connections. This is relevant not only to particular physical practice but to everyday movement in general. This is where you can start doing something about it. Most of us repeat daily actions on autopilot - brushing our teeth, pouring coffee in a cup, sitting, walking, etc. They become so automatic, you can in fact do several things at the same time, but like with any multitasking - it means you are not doing any of these things well. It is very easy not to pay attention to yourself and this is what leads to losing vitality and interest in life. The simple action of taking a toothbrush in a different hand that you are used to is already a significant change - imagine how much stimuli you receive when you perform more complex patterns with your full attention.
Variability is intrinsic to all biological systems, if we look at nature - even if from first sight things look alike, nothing is exactly the same. We form a part of nature so I believe this is where we should learn from. For human babies variability is the source of learning and wiring of the system. As we get older, it is the requierement for maintaining both mental and physical health. There have been studies made (Cai et al 2006) that have proven how lack of variability in movement prevents optimal skill aquisition. And others (Harbourne & Stergiou 2009) that link it to the necessity of aquiring new skills and adaptability of underlying systems for optimal health. The less attention you pay to everything you do, the more chance there is that the all the patterns you produce lack the fertility that your brain's soil needs in order to grow new connections, thus less and less development occurs. This is a reversable process though, you can always chose to bring your attention back to your life, even if at the beginning you might have to force yourself to do so. When you have already developed a habit of auto-piloting through life, there is a tendency to slip into the same groove over and over again.
In this article I have been talking about how movement affects our cognition. There is more and more scientific evidence that movement is the main source for our well being and an underlying process of our development. And more then anything, we now know that its quality is the ultimate catalyst in the way we evolve. Our life is shaped by the daily choices we make, even if by our nature we always prefer to look at the bigger picture and get bored by small details. Understanding what drives our choices and how it affects us in the long run is what gives us control over them, be it deciding to pay attention to your gait pattern every time you walk to a store or resolving global problems. We do not see the connection between the two, but there is a lot of evidence that there is more than we think there is. So it is up to you to chose one of those.