In my experience working with small businesses, most people seem to think you have to simply be smart to have a successful business. While being smart helps, and a good brain can make decisions easier, two other body parts are far better indicators of whether you will make it.

Here’s what matters more:

1. Your belly.
2. Your ears.

First, without fire in the belly, you lack enthusiasm. If you don’t have the passion to overcome setbacks or to motivate you through boring or tough times, you won’t have the grit required for the long haul. Entrepreneurship relies mostly on that spirit of determination and passion. And let’s face it, without enthusiasm in the world of hard work, all you’re left with is hard work. Who notices this the most? Your customers and your associates. I’ve seen fire in the belly carry businesses to success when weaker constitutions gave up long before.

Second, your ears. Without listening you can’t make business personal. Your customers tell you a lot of what you need to know. Yes, you might have to initiate dialogue now and again. You may have to pitch your product or service frequently. But in the course of business - if you’re listening - your customers will communicate the most valuable information on how to grow your business. For example, one owner may hear a customer complaint, but a successful owner hears an opportunity to improve services, introduce new features, or to make a customer for life by righting a wrong.

As president of The UPS Store, I see how important these qualities are on a daily basis. I see our new franchisees inevitably come up against scenarios they didn’t expect. I know how challenging it is for anybody to develop all the different skills - management, marketing, accounting, IT and more -- required to make even a small franchise business thrive.

But I also see people overcome those challenges. In fact, the single most satisfying part of my job is helping our franchisees cope with the always changing, always urgent demands of their jobs. Nothing is more exciting than hearing a formerly struggling franchisee tell me he or she is well over the hump and now wants to open another location.

I think I was lucky, as a teenager, to work at a small pizza joint, U.S. Pizza Co., in Little Rock, Arkansas. That’s because the business - which started as just a few tables on the site of a burned out clock shop - was run by one Judy Waller Breece.

Judy is the embodiment of what it takes to succeed in small business - and perhaps in any endeavor. When she started her pizza place she was a young 20-something, who’d grown up on a farm and possessed the salt-of-the-earth work ethic found in people with that background. Judy knew she had a lot to learn about business and her pure enthusiasm motivated her to spend 17-hour days learning it. The fire in her belly was always burning, and I saw firsthand as a teenager how she used it on a daily basis to succeed and grow.

She was always “on.” Nothing got past her. Judy saw everything her employees did and pointed out every mistake - not in a bad way, but in one that said, “Every detail is important and I respect you enough to help you do better.” It helped that she demanded even more of herself than she did of others. She did every job there was to do at U.S. Pizza - including cook.

Judy always paid attention. She listened to her customers and made it a habit to find out what they really thought of their dining experience. No perfunctory inquiries for her; she often sat down with the regulars at her establishment so she could have a real conversation with them. She believed they made her life easier when they told her what they really thought.

She was right about that too. Genuine, real-time feedback is critical to improvement. I learned that myself while in the U.S. Marine Corps, where I spent seven years before entering the business world. In the military your leaders are constantly critical; it’s part of the culture where feedback leads to improvements that may save lives. I think that helps explain why people with military backgrounds make great candidates for franchisees and small business ownership.

In any event, the likelihood that a business owner will actually get genuine, thorough feedback depends in part on the nature of his or her relationship with the customer. Having a personal tie - the kind Judy established by sitting down with her pizza establishment’s “regulars” - fosters candor.

It also nurtures the kind of relationship customers want. They want to feel that the business owner cares about them and has a commitment to their success, that the owner is their ally and champion. And for the small business owner too, much of the potential joy in the enterprise comes from establishing that kind of strong human connection. It is by no means all about the money. The satisfaction small business owners can derive from knowing they are really helping their customers and their community is immense.

But these relationships don’t develop unless small business owners make the most of their ears. Today Judy’s small businesses isn’t so small. It went from a single pizza place to 10 locations, four additional licensees, and a developing franchise operation.

It’s not all that complicated: your belly and your ears. If you enter small business with those two things going for you, you have the most important ingredients you need to flourish.