At this very moment, a significant number of people are dreaming about leaving their jobs and going into business for themselves.

These fantasies are fed by all the times we've been told to believe in ourselves, to embrace the American dream of going our own way and doing it for ourselves.

There's no doubt that leaving behind a routine job and becoming your own boss is exciting, and many of those who set off on that path find personal and professional fulfillment there.

But in any endeavor, reality is better preparation than fantasy. And when it comes to entrepreneurship, the reality is complicated.

Here are some of the things you don't hear about it--but should:

There's a dark side. The sad truth is up to 90 percent of new businesses--including entrepreneurial startups--fail within a few years. It's inspiring to hear about an Amazon or a Zappos, but the risk of not making it is real.

Passion alone won't cut it. We've heard it a thousand times: Passion will prevail. And that's true, but only up to a point. In the long haul, success has a lot more to do with less exciting character traits: patience and endurance.

It takes years of hard work to build a business. Many believe that entrepreneurship means shorter hours and more free time. In reality, entrepreneurship means building your business carefully and faithfully day by day over a period of years. If there's a true secret to success, it's hard work, period. Or, more accurately, very hard work. Being in business for yourself is definitely rewarding, but you have to be ready to work harder than you've ever worked for anyone else.

Isolation is a fact of entrepreneurial life. The thought of flying solo is exciting--but it can also be stressful and even lonely. When you work for an established business, you have a trusted network of colleagues to tap into for feedback, a safety net of shared responsibility, and the chance to connect with familiar people during the workday. Isolation is a significant factor in the lives of most entrepreneurs.

To lead others, you must manage yourself. In the popular imagination, entrepreneurship is just about having an idea. But successful businesses--even those with just a single employee--have great leadership. And the best leaders know, above all, how to manage themselves.

You probably won't get rich. Another misconception is that entrepreneurship is a good path for becoming filthy rich. The rewards are many--but if what you're ultimately looking for is wealth, creating a business is probably not the best way to go about it.

A crisis of confidence is probably in your future. Entrepreneurs are generally confident people who hold deep convictions. But for most of them, at some point, the responsibility and high stakes combine to create a devastating loss of certainty in themselves and their work. When you feel hopeless--and you will--you have to be able to work hard to overcome any self-doubt, any feeling of doom, or any situation that feels overwhelming.

Don't fake it, ever. I leave this to the last because I feel it's the most important. "Fake it till you make it" is a popular mantra, but I believe in the integrity of being what you are in the moment. The secret of success is to be yourself--flaws and all.

Entrepreneurship isn't for everyone, and that's OK.

But those with the heart of an entrepreneur will always go through life making more opportunities than they find. They will overcome more challenges than they ever thought they'd be capable of and--above all--they never confuse a defeat with a final defeat.