From all that I have read, and from my personal experience of it, yoga seems to me to be an exquisite  middle ground, found only through the surrendering of self and through the seeking of union with what might be called the divine.  If this sounds esoteric, it is not.  It has to do with finding the middle path and learning  how to stay there.   

The work of yoga, or finding that middle path, never ends.  The Bhagavad Gita  says work must be done for its own sake, and not for the end result or for a final reward.  Success and failure are to be viewed as irrelevant. This reminds me of what Kipling said in "If" (the poem so many of us had to memorize as children):  "If you can meet with triumph and disaster, and treat those two imposters just the same..." At the end of the poem, the young boy has a set of guidelines for becoming  a man (one hopes Kipling would advise a daughter in the same way).  At the end of the Gita, Arjuna has some idea of what yoga  is, where his work lies, and how to live a life compatible with what yoga demands.   

Constant work for its own sake, and the adherence to the path of moderation, bring balance into the life of the person who chooses yoga.  The key seems to be consistency and steadiness in all things:  in balancing work with rest, effort with relaxation, waking hours with sleep.  Extremes of all sorts are to be avoided.  In this way, there can be no overwork or laziness, no overindulgence or starvation.  Part of the work of the yogi is the maintaining of this balance in everyday living, something which for most of us is a daily challenge.   

Walking the middle path, or finding the essence of true balance helps bring calmness or stillness to the senses.  As BKS Iyengar says in his Introduction to Light on Yoga, "Yoga is the method by which the restless mind is calmed and the energy directed into constructive channels".  This begins to make yoga sound very much like a form of meditation, and I think that it has much in common with meditation.  My own experience with asana has often had the effect of reining in my thoughts to the point where I am concentrating on one thing only.  My mind is entirely engaged, along with my physical self, in doing the work of asana.  The more consistent I am with my practice (and I did not reach consistency until practice had become a daily routine)  the more easily I find this entire engagement, and the less likely I am to be bothered by what my senses might otherwise lead me to do or not do.  The focus of my mind seems to help generate energy in my physical body-it is as if the energy normally dissipated by the unruliness of my senses has been gathered and channeled into a single purpose.