As Eknath Easwaran notes in The Essence of the Upanishads, when we live through the senses our vital energy—our prana—is constantly directed outward until it is depleted. We are then vulnerable to depression, as we cut ourselves off from the world in an effort to replenish our prana. Thus we set up an alternating cycle of frantic grasping at the outside world and dark isolation. Moreover, a life lived exclusively through the senses leads us to identify ourselves as strictly physical beings, and to judge both our own value and the value of others in terms of such things as physical appearance and material possessions. When those things go, as they inevitably do, we have nothing to fall back on, and so we live our lives in a constant state of fear and insecurity. We exhaust ourselves in the impossible task trying to create a safe, perfect, changeless physical environment for ourselves, and react to anything or anyone disturbing that environment as a threat. Living our lives with that attitude affects both our own inner peace and the peace of our world.
So how do we use and enjoy the senses in a healthy, reasonable way? Another metaphor from both the Upanishads and the Bhagavad Gita is useful here. The body, these scriptures tell us, is like a chariot and the senses the horses. Without some kind of control, the horses will pull the chariot in any direction they choose to go. The controlling mechanism is the mind. The lower mind serves as the reins, but those alone are not enough. We also need a charioteer pulling on the reins, and that charioteer is the higher, discriminating mind. And we need to remember in whose service the chariot exists. The Lord of the chariot is the Self. Easwaran tells us that the way we cultivate the discrimination we need to keep the senses in check is through meditation. When we meditate we close off the senses for a time and watch the mind at work. We gradually develop and strengthen our powers of discrimination. And we remind ourselves that we are more than body, more than senses, more than mind. Given those tools and that awareness, the charioteer can direct the horses in whatever direction the moment requires.