In Main Street Entrepreneur, lifelong entrepreneur, business consultant and university professor Michael Glauser reveals how to achieve your dreams by implementing the nine keys of entrepreneurial success. In this edited excerpt, Glauser reveals the one thing you must have in order to launch and grow a successful business.

Marti McMahon was one of the first entrepreneurs I interviewed nearly 20 years ago. As soon as I met her, I immediately felt her palpable passion and her off-the-charts tenacity. I thought, “Surely she must be an outlier on these two qualities.” Marti told me she had three great loves: boats, people, and entertaining. She longed to combine these loves in her own business. Her dream was to own and operate a fleet of yachts that offered gourmet dining during scenic cruises of the San Francisco Harbor, which is how she came to found Pacific Marine Yachts.

Nearly every thriving entrepreneur I have interviewed has radiated the same two qualities I observed in Marti: zeal for their business and a dogged tenacity to win. Zeal is a joyful and enthusiastic pursuit of some outcome or activity. It is synonymous with passion. It’s a fire that drives the venture. It attracts members to the team, entices customers to buy, helps secure funding, and allows the startup to compete with the giants. Zeal is energy! Zeal is infectious! Zeal is power! It’s not possible to start and grow a thriving company without a hearty dose of zeal.

Successful entrepreneurs also possess a teeth-gritting tenacity that won’t quit. They find ways to get over mountains, across valleys, and around roadblocks. They simply don’t take “no” for an answer. Rather than bail out when the slope gets slippery, they do whatever it takes to make their business work. This often involves putting in long hours, making personal sacrifices, changing directions, and keeping costs down. This galvanized stance is vital to conquering the rocky road of new venturing.

Early on, I considered zeal and tenacity two separate success factors. I’ve since discovered that a blend of the two is the essential ingredient for a successful business. If you have tremendous zeal for your deal but little tenacity, the venture will stagger. The company will also stumble if you have tons of tenacity but come up short on zeal. Hence, zealous tenacity is the critical success factor.

Zealous tenacity is critical to building a strong company. This all-important ingredient for success flows from your underlying purpose, or “why.” If your driving purpose is powerful, your zealous tenacity will be fully engaged. If your primary purpose is weak, you may not have enough zealous tenacity to get through the tough times or attract the right team.

Although it takes a tremendous amount of effort to build a successful venture, this doesn’t mean the work is drudgery. When your purpose is truly inspiring and your zealous tenacity is strong, building an organization is a joyful and engaging endeavor. You work hard because you love what you’re doing. You are building your dream, creating jobs, solving an intriguing problem, etc.

This is why I hear thriving entrepreneurs say things like, “I’ve never had so much fun.” “I love what I do enough to get up at 4:30 every morning.” “This is not work; it’s play.” I seldom hear winning entrepreneurs say, “This is killing me.” “It’s far too hard.” “I don’t know if I can take it any longer.” Yet I hear these statements in the corporate world all the time. Many people are just hanging on until something better comes along. In fact, in 2014, the Gallup employee engagement survey showed that approximately 70 percent of U.S. employees weren’t engaged in their work, and Millennials were the least engaged. Worldwide, 87 percent of employees aren’t engaged in their work. Entrepreneurs, on the other hand, are the most satisfied with their careers. In my opinion, it is far better to build your own company than it is to drift along aimlessly working for someone else, even if you earn less money doing so.

While building a business can be very engaging and satisfying, let’s be realistic. You are going to have some serious setbacks and breakdowns along the way. Your initial market may not be as lucrative as you thought. You may have to redesign products that aren’t working. You may hire employees and then struggle to meet payroll. But nothing great is easy to build. Nearly all the successful entrepreneurs I have interviewed have hit bottom a few times. So it’s important to be realistic about the work required, it’s important to get excited about overcoming the challenges ahead, and it’s important to find ways to keep your zealous tenacity alive in the long run. You will need it desperately during the early stages of your business and to get through the doldrums that will inevitably occur during the life of your enterprise.