AGAIN. NO ONE who was alive forgets the first time -- where we were, what we were doing, how everthing stopped and nothing was quite the same again. Lincoln, McKinley -- they were for the history books, and in 1963, if your were 18, McKinley was ancient history. Modern American presidents lived in the White House, led the strongest country in the world and were protected by the Secret Service. Just in case. But nothing ever happened to them. They were safe. So were we, Presidents sailed, played golf, walked on the beach.

Then came the assassinations. A year ago, long before her father was elected president, Maureen Reagan told a CBS interviewer that the job he wanted was dangerous. He had made up his mind to go after the presidency and she would help him in any way she could, she said, but face it: The job was dangerous. She talked about how Reagan had vowed to find a running mate who was philosophically compatible, in case something happened. Reagan confronted the question of his own mortality and maybe, she said, the other candidates should, too. It had nothing to do with age, she said, pointing out that John F. Kennedy was the youngest president ever elected. It had everything to do with the job: Being president was dangerous.

Monday night, Maureen Reagan was again on television, this time struggling to hold on to her emotions and not doing very well at it. "Not this president," she raged. "By God, they're not going to do it to this president." Someone asked her if this meant she was in favor of gun control and for an instant the flicker of politics was in her eyes."I've often said I was in favor of ammunitions control," she said. Her solution: Americans have to get angry.

Maybe she's right. Until now, we've reacted with sorrow to the anguish inflicted on this country by creeps with guns. We've said there is only so much the Secret Service can do. Like the public figures, we've come to accept the inevitable danger of life in the public eye. We've come to tolerate violence. What good does it do to get angry?

But there is something to be said for anger. There is something to be said for an angry public to demand tighter gun control laws, to demand that loopholes in existing laws be closed so that foreign munitions manufacturers can't circumvet American laws against importing handguns by shipping in parts for assembly in American factories. There is something to be said for a little old-fashioned healthy outrage at finding out that West Germany, an ally, is allowing its munitions manufacturers to make money by arming Americans with cheap guns. Thanks a lot, Roehm family in Germany.

We think of kidnappings and assassinations as something that go on in Italy or South America. Ours is a country of laws, order, not a banana republic. But a friend of mine, who was 13 when President Kennedy was assassinated, was startled to find that her teen-age babysitter was blase about the attack on President Reagan. Teen-age children of another friend were fascinated by it. It was, he said, an event.

John W. Hinckley Jr., the accused gunman, was 8 years old and living in Dallas when President Kennedy was assassinated. He grew up in an era of political assassinations, part of a generation whose views of American politics were immeasurably influenced by its link to violence. Hinckley may be the most alarming part of this whole episode: He had normal written all over him. mPresident of his seventh and ninth grade homerooms, athlete, privileged home. By his mid-20s, a drifter undergoing psychiatric counseling, a description that fits thousands of young men. No ready motive shows up for Hinckley's actions: No broken home, no poverty, no convenient scapegoat with which to isolate him. He could be a lot of people's son.

My son, the 15-year-old, called me at work after hearing of the assassination attempt. He knows all about the Kennedy assassinations. He found the attempt on Reagan unbelievable. He said that, and then he said it was incredible, and then he swore and I said nothing. Politically, he is coming of age in America.

A new generation of young people sat by the television, watched the video replay of a tragedy over and over again, heard the popping sound of a gun and saw the blood. Those of us who are adults now are among the last who can recall when this was unthinkable.

That may have been true 20 years ago, but it's a myth now. We can react with joy that no one is dead, and with sorrow that it happened at all, and we can accept that violence is now a fundamental part of our political process. But once we accept that, the next time a Secretary Strangelove says he's in control of the White House it won't seem quite as farcical as it was Monday afternoon.

Maureen Reagan spoke for an awful lot of us when she said she felt "fury and rage and anger that in this country, this kind of garbage still goes on." Maybe this time if enough people stay angry, something can be done while there are still millions of Americans who remember when this was not the American way.