Former first lady Rosalynn Carter, in Washington to receive an award from the American Psychological Association, said yesterday she was "very worried" about what's going to happen to the average American after the Reagan administration's budget cuts are implemented.

"I think he Reagan thinks he's doing the right thing, but I disagree with him," said Carter. Asked what she disagreed with, Carter quipped, "If you ask me what I agree with you'll get a shorter answer."

Wearing a camel blazer and plaid skirt, the former first lady appeared rested and relaxed. But she did not care to discuss Mrs. Reagan's recent decision to "borrow" designer clothing, which later are to be donated to museums.

"I paid for all my own clothes," said Carter. "In fact, I insisted on it. "I really don't want to talk about the clothes," she added.

Referring to the State of the Union address, she said, "Let's talk about last night."

"I'm very concerned," she said. "When Jimmy was president, we worked so hard to be fair to all the people. Nobody knows the outcome. I'm very worried about what's going to happen to the average person -- the person without a job."

The American Psychological Association's "presidential citation" to Carter, given at the association's office, was for her work as a mental health volunteer during her husband's presidency. Carter's interest and work in mental health dates to her years as first lady of Georgia. When the Carters came to Washington, Rosalynn Carter continued her volunteer work on the national level.

John J. Conger, president of the APA, cited Carter for her "strong leadership and tireless service to the cause of mental health."

Receiving the award, Carter said, "This brings back so many memories."