Describing her first year in the White House as "a lost year -- it was not the happiest of my life," Nancy Reagan took her campaign to focus national attention on drug problems to Texas yesterday. She was here to see two programs, one at the state level, the other at the grass roots.

Texas Gov. William Clements, who met the first lady at Dallas' Love Field, told her at a luncheon he hosted that the Texas War on Drugs Program was a citizens' effort to combat "the most cancerous, insidious problem we have in our society today."

Monday's Florida visit and yesterday's Texas visit are the first in the White House's new emphasis on the more serious interests of the first lady, who came under criticism last year for what some saw as excesses in the Reagans' life style. But if Mrs. Reagan had any thoughts about that, she kept them to herself. Her only reference to her husband's first year in office was that "last year was a lost year -- it was not the happiest year of my life."

Asked to explain that, she said the assassination attempt on President Reagan and subsequently the increased security precautions had curtailed her activities.

When a reporter asked if she felt misunderstood or, as her husband had put it, felt she had gotten "a bum rap," she simply shook her head.

"I just want to talk about children and drugs," she said.

The White House is pleased at the favorable response the first lady has had to her trip this week.

"Super, fabulous," said Sheila Tate, her press secretary, of media coverage. "Everybody is focusing on the issue and the problem and that's exactly what we wanted them to do."

Dr. Carlton Turner, the president's senior policy adviser on drugs, who helped set up the two-day swing, said the first lady "has done more than any other person to bring the drug abuse problem to the grass-roots level."

Earlier in the day, the first lady told reporters traveling with her from Florida aboard Executive One that, "This crosses all lines. It's certainly the most democratic of diseases."

Mrs. Reagan said she is anxious to get more parents involved around the country and hopes that by personally calling attention to the drug problems of youth, she can make a difference.

"When a woman gets aroused, watch out," Mrs. Reagan said of a mother's concern for her children. "A woman is like a tea bag. You never know her strength until she's in hot water. A woman whose child is involved in drugs is in hot water -- as is her child." It was a line she repeated later at the luncheon with Gov. Clements.

As she stood in the aisle of the plane talking to reporters, she steered clear of discussing what support the federal government might provide.

"That's not my area," she said.

She said she had been interested in the problem "just from reading the papers and hearing about my friends' children," two of whom she identified as Art Linkletter's daughter and Carol Burnett's daughter.

But she did not pretend to be an expert on how parents should handle their children when they discover they are on drugs.

"I'm no authority on it -- on how tough you have to be as a parent. You have to keep an open dialogue, open communication with your kids, and state your principles."

She said she had been surprised Monday night outside St. Petersburg, Fla., where she visited a treatment program called STRAIGHT, to learn what a variety of drugs young people used. Some of them she said she had never heard of before, such as "mushrooms." Seeing children and parents talking out their differences before several hundred onlookers also seemed to have impressed her.

"In the '60s they were embarrassed when their children were on drugs. Now there isn't that as much. It does terrible things to families," she said.

Mrs. Reagan avoided a group of 2 dozen demonstrators protesting industrial pollution when she arrived at the luncheon. One of the demonstrators carried a sign that read: "Nancy Reagan: Is Saving Children in Fashion?" a reference to criticism of the Reagans' life style at a time of budget cuts.

At the luncheon in the luxurious Anatole Hotel, Clements introduced industrialist H. Ross Perot, whom he appointed to construct the Texas program shortly after his election. Perot's program was based on "mother power" and five basic legislative goals. They were to draft and pass laws on drug trafficking, paraphernalia shops, sales to minors, revoking licenses of physicians dispensing drugs illegally and triplicate prescription. The legislative package was passed, as was a wiretap bill, although a court challenge has prevented enforcement of the law to close paraphernalia shops. According to Clements, the wiretap legislation was passed on the basis that it related to drug cases only.

Perot, who said after the luncheon that his personal financial contribution has amounted to "quite a bit," told Mrs. Reagan how Clements had warned him there would be no government funding. "He said whoever worked with me should dig into his pocket," Perot said. "I said I'd like to think about it. While I was thinking, he announced the appointment ." Published reports say that of the $1.2 million spent by the committee in the last two years, much of it has been out of Perot's pocket.

Both Clements and Perot told the first lady they could think of no more worthwhile project for her to lead. Clements also suggested she enlist the help of other governors as she takes her campaign around the country. The first lady said she'd already thought about seeking the help of the governors' wives when the annual Governors' Conference is held in Washington next week. "I had planned on getting up and talking to them about it," she said, as part of an effort to spotlight a problem of what she calls "epidemic proportions."

Mrs. Reagan will take part in the ACTION-sponsored White House Conference on Drug Use and Families on March 22, the first of a series to be held around the country.

The aim of the conferences, according to Tate, is to spread a program similar to the Texas War on Drugs into 15 states within a year.

"Which really means finding one major leader in each state to fund much of it," said Tate.

Before returning to Washington last night, Mrs. Reagan met with members of Families in Action in nearby Richardson, Tex. Formed in response to Perot's War on Drugs Committee, the parents' group has become a model for educating families on drug and alcohol abuse