There are plenty of successful entrepreneurs, but only a few are successful enough to have massive exits. A lot of these guys keep on launching businesses, even if they could live well without making another dollar.

I've always been curious about what motivates those people to keep innovating. What are the traits that enable those individuals to continue down the path of entrepreneurship? Here are a few:

#1: Exceptional Optimism

It's easy for us mere mortals to look at someone like Richard Branson and think how lucky he is. And while most exceptionally successful serial entrepreneurs make it look somewhat easy, the trust is that they have encountered a number of setbacks. The difference is that they don't look at these setbacks as permanent ones. No matter how many companies one launches, there will be major reversals.

What sets exceptionally successful serial entrepreneurs like Branson apart is their exceptional optimism that keeps them balanced during tougher times. As Branson himself has stated, "You don't learn to walk by following rules. You learn by doing and falling over." They're not maniacally happy all the time - that would kill their desire to succeed - but their day to day circumstances don't take their eye off of their long-term goals.

#2: A Desire to Keep Innovating

Tasso Argyros co-founded Aster Data, and was one of the pioneers in the big data space. From his Aster Data experience, Argyros learned plenty about the big data category - including its pitfalls. "The first wave of big data technology did very little to make data accessible to the business, and to accelerate how easily business can use data to transform customer experience," Argyros once explained. He realized that would be where the next generation of big data companies would come in, leading him to found Action IQ after Aster Data was acquired by Teradata in 2011.

Action IQ is an enterprise software company that aims to bridge the gap between marketing and data for the Global 2000. The company seeks to solve the whole issue of customer centricity and leveraging data in the making decisions about customers, and is fueled by Argyros' dedicated to continued innovation.

#3: Self-Reliance

Being an entrepreneur is difficult; and while the exceptional optimism of someone like Richard Branson might be able to carry them a long way, entrepreneurs also have to be willing to embrace the hard work and take the bad with the good. Elon Musk was asked recently for his top tips for people looking to become entrepreneurs, and he had this to say:

"I think it's very difficult to start companies, it's quite painful. A friend of mine has a good phrase for doing a startup: it's like eating glass and staring into the abyss. If you are wired to do it, then only do it, not otherwise. So think of it this way - if you need inspiring words, DON'T DO IT!"

Being an innovator is difficult; it sometimes means swimming against the current and battling against the preconceived notions of the public, as Musk himself has experienced multiple times with Tesla and SpaceX. In order to be successful, then, entrepreneurs have to be able to shut out the outside world and focus on the mission of their company, and be able to find the inspiration from within to continue working.

#4: An Understanding That Money Isn't Everything

Serial entrepreneur Alan Levy has quite a track record in the tech industry. Prior to Skywire Networks, in the '00s, Levy created BlogTalkRadio, a digital podcasting platform, and served as its Chairman and CEO. Levy was also President of Destia Communications, a global telecommunications firm was sold to Viatel for over $1 Billion.

After realizing a successful exit selling Destia Communications, Levy took a few years off to get reacquainted with his family and get his financial plan together, and gradually began about what he wanted to do next. While Levy did achieve monetary success as a first-time entrepreneur, he soon realized that he loved so many other things about being an entrepreneur.

He loved the idea of building teams of people with completely different but complementary skill sets. Levy also loved the idea of competing against enormous, non-innovative, dominant telecommunication companies. He loved the excitement, the passion, the hard work, and the idea of that only a thin line exists between becoming great success or a great failure.

Success isn't always measured monetarily. "It's the non-monetary reasons," Levy says, "that keep the fire going."

#5: A High Pain Threshold

Matt Paxton who rose to fame as one of the cleanup experts featured on A&E's Hoarders show, cites his own pain threshold as a reason for his success. In particular, the financial pain that entrepreneurs often face. "You aren't an entrepreneur until you ask your wife what you can sell to make payroll," advises Paxton. "Instability is all I know, and I just prepare for it and expect it."

Instability and risk are just a day in the life of many entrepreneurs, and they just learn to make themselves more tolerant to the pain of uncertainty. "I've had a great five-year run," Paxton admits, "but I know I'll have another bad five-year run someday. That's just business."

How many of these traits do you exhibit? Are there any you're working on improving?