Most women don't go for it, career-wise, like the guys do. Sukhinder Singh Cassidy breaks that mold. A onetime star at Google (GOOG), where was president of Asia-Pacific and Latin American operations, she has restlessly rotated through the startup world--from Amazon.com (AMZN) to OpenTV to News Corp.'s (NWS) BSkyB to Yodlee, a financial-services company that she co-founded, to Polyvore, a fashion site where she was CEO last year until quitting over disagreements with the founders.

Today Singh Cassidy is announcing Joyus, a shopping + video + social site to purchase products (clothing, cosmetics, whatever) via a "Buy" button embedded in a video and share the shopping opportunity on sites like Facebook. Investors clearly "like" Singh Cassidy's video-commerce play: Out of the gate, she has raised $7.9 million from Accel Partners, Michael Dearing of Harrison Metals, and other angels. And yet, Singh Cassidy says she has stepped into her new venture with plenty of angst and that founding a company, her second time around, requires a greater leap than she had imagined. Over the weekend, as she geared up for the launch, she put her finishing touches on this Guest Postcard, "Facing your Inner Entrepreneur," which she wrote in hopes that other women entrepreneurs follow in her footsteps. – Patricia Sellers

Eleven years after founding my first company, I've discovered that embracing my inner entrepreneur again is more difficult than I had imagined it would be. This whole experience leading up to the soft launch of Joyus has made me think a lot about why women don't start companies at the rate men do—and why, despite the trend, here I am on my second startup.

One thing I know for sure: It helps if entrepreneurialism is in the blood. My parents, both doctors, ran a medical practice for over 30 years. My father loved running a small business. From the age of 11, I was doing his taxes. I was taught to work for myself. And it's stayed with me. My experience supports the data out there that entrepreneurship runs in the family and is fostered in families.

That said, there are a few other things I've learned about entrepreneurial success since I've been on my own and in the game:

Face up to ego risk. When I started my first company, Yodlee, at 29, the risk facing me was in material/financial terms. Today the biggest risk--the thing that could have inhibited me from starting a company--is ego risk. That's much more intangible that financial risk, but it's powerful emotionally. I think to myself, what if I fail? What if I don't figure it out? Will others judge me for choosing this path over the expected "executive" role? While I know male identities are also tied up in their work, I wonder if women take failure and all its implications more personally.

If not now, when? When I left Google in 2009, I wanted get back to my passion for building companies and find my higher purpose and  impact. I left three months pregnant with my third child. Today, with two of my three children age five and under, I sometimes think that maybe there's a better time to be taking this kind of endeavor.  But as we grow older and time grows scarce, I am seeking my highest potential, and there's no better time than now to find it.

Embrace your grand vision. Giving myself permission to be visionary has been harder than giving it to others. I'm not sure why, because for many years, vision and energy have been essential parts of my leadership style in scaling large teams. Perhaps it's because in the world of technology, you're either labeled an "executive/operator" or a "product visionary." As if it's impossible to be both. But there's little upside to not embracing your grand vision for your company. As Reid Hoffman, the founder of LinkedIn (LNKD) and an investor in some of today's hottest startups, says, it takes as much energy to think big as it does to think small, so why think small?

Know that you're a slave and master too. As an executive or an entrepreneur of great ambition, you are deeply tied to your work--and all the more so when you're the one keeping the lights on. All the women on my management team want to win--badly--and work incredible hours day and night. For women who occupy dual titles of CEO and CHO (chief household officer), the entrepreneurial life is daunting. In our family, Simon, my husband, runs his own money management firm and is pretty involved--and we have an amazing nanny. But with children who are 11, five and one, it still takes all our effort to juggle schedules. Not that building my own company will be easy in any way, but I can be the master of my calendar. Having the choice to not commute cross-country (or across countries) is meaningful. So is being able to spend two hours with my children before they go to bed and answer emails and phone calls afterwards.

Permit yourself to be irrational. In some ways, there is no rationality in being an entrepreneur. You are trading direct and perhaps major impact in a job you currently do for potential greater impact, but the statistical probability is that you will fail. I love data and have been trained in data-driven cultures all my life. But by choosing to start a company again, I've had to come to peace with allowing both sides of my brain--the creative and the analytical--to participate in the process.

And after two decades inside entrepreneurial companies, here is the most valuable lesson I've learned in deciding whether or not to take the plunge: The greatest risk lies in not giving yourself the full chance to make it.

You can check out Joyus at www.Joyus.com.