"You have to be a certain kind of person pursuing a certain kind of objective," says Jan Zupnick, president of the Entrepreneurial Institute. Arnold C. Cooper, professor of management at Purdue University's Krannert Graduate School of Management, who is tracking the ups and downs of 4,800 entrepreneurs over three years, says, "One man told me, 'You wake up in the middle of the night and you wonder if you're crazy.' " Cooper says that while crazy may indeed be a characteristic of some entrepreneurs, there are more prevalent ones:

*Drive. "The need for achievement," Cooper calls it. Lynn Gilbert of Gilbert Tweed Associates Inc. says, "You have to be driven to succeed, driven to do it better than the next guy, driven to take control of your life."

*Energy. Says Cooper, "You've seen the guy who says, 'Gee, I didn't get anything done today. Am I glad I'm not working for myself.' Well, the entrepreneur does." Kathy Kolbe, president and founder of KolbeConcepts, says that makes good health essential: "It's devastating to be sick or down for any reason."

*Self-confidence. "It's constantly being said that I've done everything I've done without credentials," says Kolbe. "It's as if I'm thumbing my nose at those who have gone before me and I'm going out and blazing new trails. Well, that's exactly the point."

*Objectivity. Despite an overwhelming belief in their idea, product or business, those who make it keep on course with reality.

*Perseverance. "You're going to stumble a lot, you're going to bruise yourself a lot, and you're going to get bloody," says Gilbert. "But you have to keep getting up."

*Flexibility. Says Craig Barzso, founder of Concept Development Associates Inc. in Bethesda: "Flexibility, maybe to change the whole nature of the business in 30 days, is the one advantage we have, so you've got to be able to use it."

*Vision. "You have to be able to see beyond the day-to-day," says Kolbe, "to get beyond the frustrations and work toward your goal." Adds Zupnick: "Entrepreneurs are looking to build something for the future, not to sell the next pet rock. Money is how they measure their success, but it's not their motivation. To control their own destiny is the motivation."