IHAVE a guilty secret: I keep wanting to be an Old Lady. At 87 I surely qualify, but in the great warren of retirees where I live it is simply not allowed. We septe-and octegenarian females are "senior citizens," complete with rights and pantsuits; to approximate youthfulness is our goal. By the example of my friends, by my shame to be a quitter, I am obliged to go on -- and on -- being "young."

I must dress young. I may look like mutton but I must get myself up as lamb. If I am to see my friends, I must attend meetings and lectures, for they will all be at them. A club for everything, and everyone in a club. Social life must be pursued, and even romance is not quite ruled out -- a casserole carried to a newly-widowered neighbor being the common ploy for that. Body as well as mind must be exercised, at pool or links, and I must never, never get fat.

It is all so laudable. We are abreast of the times, on the ball, cool. Why should I think wistfully of the different life once lived by the grandmothers of my childhood -- by no means replicas of Whistler's Mother, but unabashed Old Ladies to be sure. I remember them well.

As a group they were easily distinguishable; no male eye was ever deceived by a rear view. They dressed in black, a white ruching at the throat, and should a neckline swoop below the collarbone, a guimpe of net and small whalebones carried decorum almost to the ears. Among the more dressy, a long chain might support a lorgnette or a fan, which, when in use, made rhythmic and agreeable slaps against the bosom. Shawls were kept near and Louise Canby lives in Silver Spring. rubbers handy for any excursion into the damp beyond the porch.

Their days were spent at home, sitting. Oh, how they sat. They sat upright in straight chairs; they overflowed cushioned rockers. They sat to sew on buttons and to darn socks, on the back porch to shell peas, on the front porch to observe neighbors. They sat to rock babies and to read to older children, starting with "Mother Goose" and "The Wizard of Oz" and continuing through "Black Beauty" to "The Wind in the Willows". Mass sitting was achieved -- by the fortunate -- on the verandas of summer resorts, where the Rockingchair Fleet, that redoubtable assembly of their contemporaries, gave welcome relief from the three-generational household which was their inevitable habitat, for of course they lived with one of their children.

And there's the rub -- an acid test we do not have to pass today. She who had been a major-general in her own home found herself of a sudden -- all love and consideration notwithstanding -- with no more authority than a corporal. The daughter (it was usually a daughter who took over) was caught up in a whirl of children's music lessons and dental appointments, possibly in causes which to the mother seemed odd if not revolutionary. Mealtimes could be erratic, and the food likely less in accord with what she had taught her daughter than with what the son-in-law's mother had fed him. Confusions; endless adjustments.

There were many grandmothers who passed this test cum laude and became a benediction in the home, but it could not have been easy. Oh, no. My private burrow in this warren is much better, my independence precious. I will recant my heresy and give proper thanks for my freedom here to live exactly as I please.

Then why this unfulfillment? Independence, did I say? Independent as a sheep! In my dogged pursuit of youthfulness I have embraced youth's weakness: I have yielded to peer pressure. I have been a sap. Why should I make myself keep up with the swim when what I really want to do is slump? What harm in idle moments? I want just to sit for a bit, look out the window at the buds bursting, the snow falling, the squirrels robbing the bird feeder. To label old family photographs. To reread "War and Peace" and finish "The Decline and Fall . . . ," diluted with whodunits.

Of course, I will keep up the bit of volunteer work I still am good for, read the news, follow the fortunes of my favorite team, and it is possible that in doing it, I shall still have one toe in the swim. All this is only what it truly pleases me to do. For is not "natural" the ultimate in modern slogans -- the one which rules all cereal ads, inflates the value of certain fabrics and justifies the free rein given the whims of children? I shall embrace that word, do what is natural to my age, and be a Natural Old Lady.