A friend of mine, whom I'll call Erin, married right after college. When her husband was in graduate school, he surprised Erin by suddenly announcing that he wanted to start a company.

Erin admittedly wasn't happy about giving up their well-laid plans to buy a house, have kids, and live a fairly routine life. But she still did what she had to do to support her husband's venture, including staying in a job she didn't like to pay the bills and even moving to Asia so he could work there.

Then, six years after the company started, Erin discovered a love letter on her husband's computer from one of his female colleagues. The letter referenced an extramarital relationship that had been going on for two years.

When Erin confronted her husband about the affair, he didn't deny it. She asked him to cut off ties with the other woman and enter couples counseling with her in hopes of saving their marriage.

Her husband refused. He wanted a divorce. The papers were filed within a month.

How being an entrepreneur can create marital problems.

When I shared Erin's story with therapist Chris Bruno of Fort Collins, Colorado, he wasn't surprised. Chris is an entrepreneur himself and has worked with many entrepreneurial couples. He painted two scenarios that could lead to serious marital problems for entrepreneurs, up to and including infidelity.

  1. When spouses work together on a startup, the risk is that "everything they're doing together in the relationship has to do with the business," Chris explained to me. "The marriage has been put on the back-burner." Given enough time, the love and intimacy in the relationship fizzle. The spouses find that they have become business partners and nothing more.
  2. The other, more common scenario occurs when one partner in the relationship is an entrepreneur and the other isn't. "One person is the business person," Chris said. "The other person is left with everything having to do with life and family and relationships." Their lives become so separate, and the relationship so infected with resentment, that both spouses are tempted to turn elsewhere for affirmation and a sense of connection.

Startup life provides motivation and opportunity.

A longtime Silicon Valley investor I know has seen this over and over again with the entrepreneurs he works with. They become overwhelmed with travel and work, and end up spending far less time with their spouses than is ideal.

"A lot of resentment builds up in the non-entrepreneurial spouse," he told me. "He or she wants their spouse to be home more, but all they seem to care about is work."

But he's seen plenty of entrepreneurs struggle with resentment as well. "They think, 'I'm working so hard for us, for our family. Can't you see that?'"

Psychologists have found that people most frequently have affairs because they are seeking sex, emotional sustenance, or love. Unfortunately, the startup life--with its crazy workload and all-consuming nature--provides a perfect setup for infidelity.

If one spouse is expending all of his or her energy on a business, the other spouse is likely to feel less loved and appreciated. That's the motivation to find love and attention elsewhere.

And the many hours spent away from one another in vastly different worlds? That presents the opportunity.

Your marriage only needs five hours a week to thrive.

If you've been around entrepreneurs, chances are you've heard stories of cheating spouses. In the general population, about 10-13 percent of married individuals say they have engaged in infidelity. Though studies haven't been done on entrepreneurs and their spouses, the percentage of those who have cheated is likely higher.

Fortunately, it is possible to maintain a healthy marriage while building a company. You just need to be willing to intentionally invest a few hours a week in your relationship.

In his bestselling book The Seven Principles for Making Marriage Work, longtime marriage researcher John Gottman contends that couples don't need that much time together to stay connected.

Based on his research, he says couples can maintain a strong relationship by spending just five hours together each week through intentional partings, reunions, end-of-day debriefings, appreciation, affection, and a weekly date. He calls this the Magic Five Hours.

In the 168 hours available in a week, setting aside five hours for your marriage isn't that much. But doing so can vastly elevate the level of intimacy and communication you experience in your relationship.

With this modest yet intentional investment, you hopefully won't need to look elsewhere for love. And your marriage won't just survive the startup life, but it could very well flourish.