There is a popular old legend that a person only uses a fraction of his brain. There does not seem to be any science behind this myth, but the idea that we have more capacity than we are aware of is attractive to people. It stems from our being witness to tremendous feats that people can accomplish with their bodies. At first glance, their bodies look a lot like the bodies of others, and yet they can stretch, flex, train, and push their bodies to do things that surprise and amaze us. From there, it would seem like a small leap to the notion that we can flex our otherwise similar brains and accomplish amazing feats with our brain, as well.
There is not much to support the body-brain analogy, as attractive as the idea might seem. But the idea of stretching ourselves to release the potential in us remains attractive and should be pursued. People who climb want to see how high they can climb, swimmers want to see how far or fast they can swim; runners want to know just how quickly the human body can run a mile.
And if the body-brain analogy is weak, there is a great deal to learn from a body-soul analogy. Most people utilize but a fraction of their souls. And there is a very high price which we pay for neglecting our soul. In the case of the body, we suffer from atrophy and loss of tone if we do not utilize the capacities of the body, but there is not much proof that we gain longevity or the like from being a body-builder. Going beyond the basics to body-building is primarily driven by the desire to know just how far a person can stretch the capacities of the body. With regards the soul, there is a parallel atrophy which sets in if a person does not utilize all the parts of his soul. But, in contrast to the less-clear benefits of becoming a body-builder, there are profound benefits from becoming a soul-builder, and those benefits go well beyond just knowing how far one can go in utilizing his soul.