"A wise person could live happily in a trash heap ." -- Epictetus

William Nickels is stuck in traffic. An accident has jammed the Beltway, he's trapped behind a busload of screaming kids and he's going to be late for his job at the University of Maryland.

"My mind tells me that this is awful," says the 41-year-old marketing professor. "This is not where I want to be; this is upsetting."

The growing tension sets off a tiny alarm in Nickels' brain, which triggers his personal mind game: "I ask myself what else I could be doing now. I answer, I could be grading papers or writing a report.

"But if I were doing that, what would I want most? I would want to get away from my desk, listen to some good music and relax. And that is what I am doing -- sitting in the car, listening to music. Now all I have to do is relax."

Score another win for Nickels in the life contest he calls "the happiness game." The major skirmish, he contends, "is always between you and your mind. It's not the reality of life that counts, but your reaction to it."

Although his profession is teaching marketing (he's rated as one of the students' favorite professors), Nickels has made his life work happiness -- the result of a 6-year "happiness quest" brought on by watching friends hit mid-life in misery.

"My wife and I traveled across country to visit old friends. Each person we visited had reached childhood goals and found success, but not happiness.

"One who had struggled hard to become a surgeon confessed he'd sacrificed friends, family and fun for medicine. When he was ready to turn his attention to those other areas, they'd atrophied from neglect.

"Another was young, single, president of a ski club, launched on a great career. But he admitted he was being pressured at work and didn't like his job."

The problem, says Nickels, is that "people confuse happiness with success. They work hard to achieve success, because it's supposed to bring them happiness. That's called 'Making It.' . . . 'The American Dream.' But this country is filled with successful people who are miserable. We are obviously buying into a flawed system."

Nickels was "shocked" at his friends' misery "because I was brought up to place a priority on happiness. My father (an insurance salesman) would take the day off if it was particularly nice outside and take my mom and us (six) kids driving in the country.

"Dad knew the importance of a balanced life. He enjoyed his work, but kept it in perspective. He never took a job as a sales manager because it would take too much time.

"We never had a lot of money, but always managed to take a nice vacation. He's 70 years old now and still going strong -- he and my mom just got back from Hawaii. Everyone asks him, 'How do you do it, Jack?' "

Answering this question -- how his father stays happy and how others can, too -- became an obsession for Nickels. He devoured scores of self-help books and attended several "human potential" courses, including est -- which, despite friends' warnings ("They swear at you, they don't let you go to the bathroom"), he found worthwhile.

"I tried to encourage friends to go," he shrugs, "but they resisted. People don't want to take self-help classes because they consider it an admission that things aren't working for them."

So Nickels extracted the essence of what he learned on his "quest" and wrote The Happiness Game (Acropolis Books, 183 pages, $11.95), "a complete," as he calls it, "personal development course you can do at home."

Nickels structured the book as a game "because I find it fun to approach life as a contest. The only competition is between your score now and your score later. The basic goal is to experience happiness."

Most people aren't happy, he claims, because "they play the 'I'll-be-happy-when' game . . . as in 'I'll be happy when I get the right job.' or 'I'll be happy when I have a Mercedes.'

"They think they're unhappy because they lack something, so they work themselves ragged to get it. But when they've gotten it, it doesn't make them happy, so they think they lack something else.

"The only time you can be happy," he says, "is now. Many people are so busy thinking about the past or the future that they don't enjoy the now. But the time they spend regretting or worrying could be spent living.

"One of the Iran hostages -- Moorhead Kennedy -- realized this. When everyone asked him if it was a horrible experience, he said, 'Oh no. I lived each moment in terms of right now.' "

One problem with discussing happiness, says Nickels, "is that people mean different things by it. Most people think of joy, bubbliness and fun. And there's something about our ethic that makes this seem frivolous, or irresponsible."

Nickels defines happiness as "the ability to appreciate fully who you are, what you have and life the way it is now. That's not selfish. You can't feed someone else if you're starving to death."

Even death, under Nickels' terms, "is part of the adventure of life. It's like walking through a jungle and getting scared by a lion. Without that experience, the trip wouldn't have been as exciting."

So is he happy?

"Nobody is happy. It's not some state you reach and stay there. Happiness is a decision, a choice you make moment by moment. Yes, right now, and most of the time, I'm happy.

But sometimes "I give in. I just go in the bedroom, shut the door and worry."