For a moment, the woman across the table looked drained of energy. If she were the sighing sort, she would have breathed out the closing line of our short conversation.

Instead, she spoke in a careful voice, "All I know is that I'm in the same movement for the second time in my life and I'm not even 40."

The sentiment was a stark and simple one. The woman who had claimed some victories for the causes of her 20s and early 30s was now watching the territory erode. She felt no momentum for her "side," had lost any illusions about a swift "win." The second phase of this struggle would be, she suspected, to hold the old ground, trench by trench.

Her words over lunch resonated in my mind. Though she spoke them in Denver, the same feelings were repeated all along the way from Colorado to California last week. I met people realizing that they would have to fight again for the turf they thought they'd already won. And wondering if they could.

The woman in Denver was talking about women's rights, but she might just as easily have been talking about the environment, peace, civil rights, human rights.

In Phoenix, a woman active in the anti-Vietnam War movement talked with disbelief about our increasing involvement in El Salvador. "Didn't we learn anything?"

In Los Angeles, an environmentalist who drives home through smog as dense as the fog of Cape Cod, talked about the undermining of the clean air deadlines. "It's going backwards."

In San Francisco, a civil rights activist shook his head at the critical words in Reagan's budget speech. "The taxing power of the government must be used to provide revenues for legitimate government purposes. It must not be used . . . to bring about social change."

What is a legitimate government purpose if it isn't social change for justice? he asked ardently and then reflected on his own heat. "I've said it all before. I've heard it all before. It makes me so damn tired."

Tired. It was the word I heard most often -- even more than "angry" -- when I talked with people called liberals, who had done time in a movement to help the poor or end the war or clean the air. People who thought they had built something solid now feel the ground crumbling, as if it had been staked on sand and not hard rock.

As Sen. Paul Tsongas says again and again, "The last election changed things. Not only did we lose Democrats and liberals but those who are left are so weary."

Weariness is not just an occupational hazard of politicians. It also infects the legions of those who care and cared . . . and now often call their own belief in swift victory "naive."

It hits the generation that came into adulthood in the '60s hardest. They saw their piece of time as a straight line instead of a cycle. They saw progress as an arrow instead of a pendulum. I suppose it is only the young who believe that points stay proved and fights stay won. We are all unencumbered by history until we become part of it.

Now we know that some of the movements were nourished on heady air but had weak roots. We know that some have never survived hard times in our country. We know that some simply have strong enemies. And we know that it all now hangs in abeyance.

So today, one woman wonders whether her daughters will look back on Their Mother the Feminist the way another generation looked back on Their Mothers the Suffragettes: as terribly quaint.

One man who was there at the anti-Vietnam March on Washington wonders whether his children will think of it as some national rock concert.

Another who truly believed that we should -- would -- create a social policy based on justice wonders whether this idea will be recorded as a historical oddity.

They know that the answers depend in large part on whether they learn the lessons of the old activists who learned in lean times how to regroup, change, keep a structure and dig in for a long haul.

But it also depends on how you find the energy when you are in the same movement for the second time and you're not even 40.