Sometimes the pain is hers. Sometimes the pain is his. Sometimes there isn't any pain, but that's comedy, not romance .

The wonder of it all, of course, is that we continue to go on with it, even in this town which thinks little of lightweights and lunacies that can't be legislated. Administrations change, races are lost, but it's still the same old story and here are a few of them. Changes have been made in the names and identifying details of the participants .

They were brought together by the inefficiency of the federal bureaucracy; both over 65 and retired, they met in a line at an office of the Social Security Administration, and in the time they spent waiting together (more than an hour), they decided it was love at first sight.

Both were widowed and they wanted to marry, but the bureaucracy that brought them together also kept them apart. Under the regulations in force at that time, she would have lost her widow's pension if she had remarried, and two would have been forced to live as cheaply as one.

Could she move into his home? Social Security would mail her check anywhere. Could she change her name to his? Social Security didn't care what name she used, as long as she wasn't remarried.

The solution was obvious. "My mother would have called it 'living in sin' and would have been horrified," she muses. "My son calls it 'shacking up' and thinks it's funny. We just call it getting along the best way we can."

Regulations have now been changed, so that they could be married without suffering a financial penalty, but it's too late now. "If we invited all our friends to a wedding at this point," he says, "we'd just be informing them that we weren't married before."

They accept their situation philoso-phically and find that, for them, living together is less complicated than for younger people who seem to take such arrangements for granted.

"One advantage of living together at our age," she notes, "is that when you check into a motel, nobody asks any questions." CAPTION: Illustration, "William, do you have the courage to love?" Drawing by Koren, Copyright (c) 1977, The New Yorker Magazine Inc.