As recently as a century ago, when the average life expectancy throughout the Western world was less than forty years, people gave little thought to keeping fit. Life was simply not long enough. The few men and women who lived into their eighties and nineties were thought old souls of whom it was said that they were so mean nothing would kill them.

Today the picture has changed. On the one hand, science and medicine have combined to lessen the hazards to which we are exposed. Plagues have been wiped out. Anti-biotics and other miracle drugs are conquering diseases long considered incurable. Surgery is capable of life-saving magic. Our life expectancy has very nearly doubled and continues to rise.

On the other hand, we have acquired an entirely new set of problems. Even as the years of our lives stretch out longer, existence becomes infinitely more complex. By its very nature, twentieth century civilization makes this inevitable. The Atomic Age is hardly a relaxed age. We circle the globe in a matter of hours, we talk of trips to the moon as the reality of tomorrow - but we also know that tomorrow's wars, unless prevented, will be on a scale to wipe out continents.

On the personal level, our urban civilization brings with it tensions virtually unknown in our grandparents' time. We tend to live on the run, geared to split-second timing, to noise, to newscasts every hour on the hour, to phones jangling and cars honking, subway trains, deadlines and keeping up with the Joneses and seldom sufficient rest, relaxation or sleep. None of this is conducive to peace of mind. As for our physical conditions, as fast as the human body is enabled, through technical advances, to last longer, it falls prey to a new, totally different roster of ills.

Look around you and compare the medical picture with what it once was: Smallpox has all but vanished, tuberculosis is rapidly being wiped out, pneumonia rarely kills, and death in childbirth is no longer something to fear. But now it is the diseases of old age and of tension that are the evening. Today heart trouble is the number one killer. Ulcers, arthritis, allergies, and allergic respiratory disturbances - not to mention mental illness of every variety - plague the young, the not-so-young and the elderly.

But since the world we live in is the only world we have, and since we cannot individually do much to change it, the next best thing is to learn to adjust to it with some degree of comfort. True, we cannot very well go bucolic, escape to some Thoreauvian Walden, some Shangri-La of our own making. Nor can we shut our eyes, close our ears, and turn off our emotions enabling us to remain impervious to the life around us. We probably wouldn't want to do that even if we could, for whom but a born hater would deliberately choose indifference to those very qualities which make us warm human beings?

Fortunately there does exist an answer to this problem. It is possible for anyone who will only take the trouble to learn to live serenely in our Age of Anxiety. Within easy reach is a key to living out one's allotted span of three-score-and-ten or more, enjoying all the while a vigorous mind in a vigorous body, both of them functioning to the very limit of their potential. The key to such well-being is Yoga.