"NEVER LIVE with your children," my wife of 40 years cautioned. When she died I lived alone for a few years in the same house. It was never the same house.

If it was lonely in the early day, the evenings were worse-like the Sundays I suffered when, as a salesman, I had to spend them in a hotel on the road. Walking along in the hall past the children's bedrooms, I'd peek in sadly. The beds were made up neatly, unused and silent. The phone my daughters were once constantly on was mute, constantly off.

From time to time friendly real estate people rang my bell at odd hours. I sprang to life. I listened to their condolences. I wasn't ready for this empty living, and I wasn't ready to sell my home. Not just yet. Wait, my son-in-law advised me. My son suggested a trip to get over this period.

A few months went by. My children were wonderful, so caring. Time would burn up the past. I took a 10-day trip through Norway, alone. I found out half my problem was the language barrier. The other half, when I couldn't distinguish between Bergen and Olso, was me.

When I went home I leased my house for a year, then drove by myself to Chicago to visit a lifelong friend. His wife had been dead a few years; he was living alone and, from what I could gather, wanted it that way. He told me his adjustment and transition had been a problem, and I had an opportunity to discover his manner of living. As a lawyer he just plunged into his work. He lived mostly for his work-simple for him.

After a month with him in Chicago, I decided to visit my brother and his wife in Los Angeles. They had pleaded: Come out to stay! The visit was short; they had a 16-year-old daughter and a huge family dog. I loved their child, the dog hated me back. So much for living with friends and relatives. I flew back home after a week.

Eventually I would have to face the fact that I was lost, rudderless. I just wanted to get away from my home where I had lived for 24 years. It was lonely and too full of memories of my wife.

I HAD A TRY living by myself in Memphis and decided my unhappiness was that I was lonesome for my children, family life and their daily contact. Of course all three of my children were married, had families of their own. Two lived in Washington, D.C.; my oldest daughter, a teacher and writer, and her doctor husband lived in a 22-room house in Brookline, Mass, with one son, aged 7.

I visited with them. They had plenty of room and had leased out their third floor to two students. When the semester was up both students left town and returned to their homes. My daughter suggested I lease out their apartment.

"Never live with your children." I remembered my wife's words. I suggested that my daughter first talk it over with her husband. Only if he were happy with the idea would I move in; the plan appealed to me.

We decided to experiment for a six-month period. At the end of that time we could decide if we should continue the arrangement. I paid my rent for six months and moved in.

Living with my daughter, my son-in-law and my grandson, Adam, was something new, an experiment and a challenge. I had the entire top floor, and my own furniture, which I had shipped from Memphis, made it very comfortable. I was beginning to feel like my old self again. Respect and privacy helped, and since my daughter and son-in-law both worked, I had the advantage of using their home during the day.

Retired grandparents have lots of time, leisure to spare. I became available, anxious to be part of the family. I wanted to be home any evening for baby-sitting, happy with the thought of being close to a bright grandson. One flight down, he gave me many hours of pleasure. He came with the territory, visiting me while I was painting. He would share my acrylics, and we'd paint together.

Once, while I was helping him draw and paint, he said, "Pop, mother says you are a writer-how come you are painting?" I looked at my 7-year-old grandson, one of my first discoveries of my new-found happiness, and said, (I was so full of love for him at that moment, I hesitated): "I am a writer, but no one will buy or print my stuff; no one will read my stuff, my stories." "Grandpaw," he said "I'll read your stories." Oh, I thought, I hoped I could always enrich his life; he sure has been a treasure-pot for me.

THAT'S HOW living close to my family has been. Once Adam came up for a visit to present a hand-crayoned Valentine, a red heart. Across the center he had lettered, "Guess what day this is?" So you live all these 75 years and suddenly, like Alice in Wonderland, you're in a new world. From time to time I heard him learning to whistle. When is the last time, or the first time, you have heard a kid whistle? It's happiness. Forget the pains, the problems. There you are, sharing his pleasures. Listen to his questions. Grandchildren are loaded with questions. I have to be ready to discuss the Red Sox, because he says he wants to be a ballplayer when he grows up.

Folks at home can adjust where there is caring, loving. I have grown closer to my children, and I'm thankful I'm able to move about for myself. It's been almost four years since I moved in. I always think back to the lonely times I had trying to find how to live alone, the lonesome nights.

For really no reason, I decided (I hinted) one day that maybe after four years I might move. After all, Adam is almost 12, and, well, four years is a long time for a husband to be with an in-law. Last year, four months ago, my daughter told me she and Terry, her husband, were thinking of having another child. At 35, if she was going to have another, . . . well, would I stay if she got pregnant again? Such a delightful challenge-request, if you will. Indeed, would I stay! A command performance.

How often does such an honor come your way? A lifetime proposition. After learning how to make a great after-school milkshake, I found out that today's diapers have done away with the safety pin. What a pleasure to learn that living with children is learning again to live for them. Up on my kitchen wall I have crayon drawings of flying first basemen, and Valentines reminding me what day it is (and no more lonely nights). It's Grandfather's Day. CAPTION: Illustration, no caption, Pictures 1 and 2, Lloyd Stern (left) as a high jumper for Butler University's track team in 1928 and with his grandson, Adam.