Norm Brodsky, a coach and member of the New York chapter of the Inc. Business Owners council, is fond of saying, "As an entrepreneur, you'd better be successful because you're unemployable otherwise." And while he says this in a loving, nurturing sort of way, he reminds every CEO in the room there is a substantial cost of being an entrepreneur.

Once you've gone out on your own, it's hard to work for someone else.

Anyone can have the "entrepreneurial spirit," but there is a seismic shift once you decide to put it all on the line. The moment you walk away from a solid job in a larger company to start something new and unproven, it's really difficult to go back. This is why Norm Brodsky refers to entrepreneurs as unemployable: Once you work for yourself, and become accustomed to calling the shots and making things happen in a way that is unique to your perspective and life experience, working for someone else becomes challenging.

Trading your evenings and weekends in the pursuit of something great.

The most obvious cost of being an entrepreneur is time. While everyone working in the corporate world today is all but expected to work more than 40 hours a week, for an entrepreneur there is an internal drive that is like no other. If you've started your own company or joined a startup, it's usually because you see the world from a different perspective and are driven by an innate sense of purpose. That passion often comes at the expense of leisure and downtime.

Burnout and exhaustion are very real risks to the business.

Especially at the early stages of a startup company, when the founders are expected to be the "chief cook and bottle washers," the desire to not drop balls pushes you to new levels of workaholism. As the head of sales, strategy, operations, finance, production, administration, technology and everything else, you are expected to seamlessly flow between diverse roles and responsibilities -- it's a tall order regardless of how many hats you've worn previously.

Survival is unacceptable.

Just getting by is not why you left a comfortable career track, so mere survival is frowned upon. The objective for the entrepreneur is to thrive; to demonstrate a new way of doing things which, when successful, is clearly the way we should have been doing it all along. When purpose is realized and demonstrated, the company scales to the level the entrepreneur had envisioned (and beyond).

Grit is the key attribute that determines success.

With all this in mind, what determines a successful entrepreneur from one of the many businesses that fail? According to Brian Levenson, CEO and founder of Core Mental Training, it's more important to have "grit" than "grind." He was moved by Angela Lee Duckworth's now famous TED Talk, "The key to success? Grit," in which she states "Grit is passion and perseverance for very long-term goals. Grit is having stamina. Grit is sticking with your future... for years."

While most people think that successful entrepreneurs must be willing to grind it out, both Levenson's and Duckworth's studies have shown that grit (not grind) is what makes the difference. Specifically, your ability to persevere over the long-run and thrive despite all kinds of unplanned events.

Some specific examples of grit include:

Using a problem to bounce forward (not back)
Celebrating the small wins.
Maintaining a healthy attitude toward misses. 

Given the same events, there are wholly different attitudes and perspectives that determine your outcomes. Grit is about having the right perspective, the right attitude, and celebrating the small wins. While the cost of being an entrepreneur may be high, that sense of purpose combined with a healthy dose of grit will ensure your long-term success.