You are a marvel of optimization. The more you do something, the better you get at doing it, it's an amazing thing to develop. The problem, when it comes to growth, is that one of the ways that you get better at it is by getting more efficient, so you put in less effort, and against a growth goal, you get less reward from it. Conversely this same optimization is great for your ability to perform that one thing well, fast, etc.

 

Lets imagine that the only exercise you do is running. When you start out, your body is working all over the place, it's something that's tough to do for you. As you run more and more, your body begins to optimize, as you run, the focus become sending blood to your legs and feet, so less gets diverted to your arms, or your head - which greatly increases the rate at which the oxygen is taken from your blood by the parts that need it - resulting in an overall mix going back to your lungs which is more oxygen depleted. This means that you can gain more oxygen from that fresh lung full of air than you could if the blood hitting your lungs had more oxygen in it. Consequently, your body through repeated focus on performance of just your legs has adapted and made tradeoffs to increase your ability to run, but at a cost to, for example, your ability to swim for prolonged periods.

 

If your goal is to become a distance runner, this is a great thing, but if your goal is to achieve a broad definition of overall fitness, this isn't a great thing at all.

 

So, for overall development, we want to ensure that we work with variety, that we don't allow the yom, ons, or sni, to get into these patterns of optimizing with shortcuts. We want to grow and broaden our capabilities in a wide variety of areas.