My mother always says there are problems, and then there are troubles. Problems are hard, but most can be solved. Troubles take you down. Sometimes they take you out. Gary and I began the millennium flush with troubles.

In 2001, I learned I had advanced breast cancer. Six months of "the killing cure" ensued: surgery, chemo, and radiation. Just as I was finishing my treatment, Gary's two brothers entered the hospital. The twins were born with a rare form of muscular dystrophy. By the time they reached age 39, their heart muscles had become irreparably damaged. I made it through fine. Gary's brothers both died, in early 2002.

As he was coping with my illness and his brothers' deaths, Gary was in the midst of protracted negotiations with Groupe Danone to sell part of our business. Stonyfield Yogurt relied on Gary's energy and ideas to move forward, and the Danone deal required his unwavering concentration. But running back and forth to hospitals scrambled Gary's schedule and diminished his focus. His mind ricocheted between high-level problem solving and existential dread.

A loved one's serious illness can absorb an entrepreneur's energy and concentration for months or years. Those who back-burner their businesses for that long risk losing them, even as medical bills mount. And, of course, entrepreneurs are as vulnerable to disease as anyone else. I recently read an online article in which company owners listed characteristics essential to success. Good health was right up there: Many described themselves as people who "refuse to get sick." Illness equates to weakness, which is antithetical to the entrepreneur's self-image. He starts off defiant, but the disease wears him down. The body gives the spirit only so much autonomy.

Illness is the rudest awakening to the dream of entrepreneurial control. All those mechanisms meant to balance family and the business collapse. Priorities are reshuffled when instinct (must care for self/loved one!) rams into expediency (must preserve paramount financial and psychological investment!). The fear of losing everything is compounded by the fear of losing everything.

When it comes to being bad patients, doctors have nothing on entrepreneurs, who believe they can heal themselves the way they do everything else: by force of will. The business owner simply reframes her condition as another set of numbers to beat or an unexpected downturn that requires an aggressive response.

Krissi Barr, founder of Cincinnati-based Barr Corporate Success, took this approach to coping with early-stage breast cancer. "I am quarterbacking my treatment the way I would a project at work," Krissi told me. Her company, a strategic planning consultancy, is growing; her calendar is full. But Krissi is her shop. When she's not working, there's no revenue. So she found an oncologist who let her schedule chemo around client meetings and speaking engagements. When Krissi's oncologist told her to cut back, she did—on volunteer commitments, not on her business.

Krissi's husband, Dan, accepts his wife's decisions. "It's good for her to stay determined," he says. But other families argue that illness nullifies all prior agreements over how much the entrepreneur will work. The husband who grudgingly accepted his wife's long hours now agonizes that they threaten her health. Yet if he insists she put her dreams on hold, will he crush her spirit and breed resentment? If he begs her to step away from their sole hope for financial security, does he court greater calamity?

Jerry Gonzalez, founder of the food company Maria Elena's Authentic Latino, in Valencia, California, was found to have Stage 4 colon cancer in 2007. Convinced he must stick with the start-up or lose it, he continued taking sales meetings and dragging himself to the office. He is now free of cancer but fears its return. "I feel as though I'm in a race," says Jerry. "I need to get my family on sound financial footing."

Karen Gonzalez, Jerry's wife, feels differently. "My thought is, Are we wasting time?" she says. "Should we give up everything—have a slower pace of life away from L.A. and spend quality time together?" Karen worries that stress and long hours will precipitate the cancer's return. Yet she understands that what threatens her husband's life also gives that life meaning.

The stress intensifies when leaders keep their conditions secret. "Sue" runs a company with her husband, "Jay," who suffers from debilitating depression. Sue doesn't feel she can level with their employees. But sometimes Jay's affliction is so obvious, she assumes everyone must know. When Jay descends into his private hell, Sue covers for him—doing his work, making excuses for his absences, and reviewing all his decisions. Even when Jay is well, she buffers bad news, fearful lest some small setback trigger months of incapacitation.

Sue's and Jay's desire to hide his condition means they have few confidants and little support. Of course, the person with whom Sue would naturally share the heaviest burdens—in business and in life—is lost to her.

The entrepreneur's confidence that he can beat his illness doesn't extend to the illness of a loved one. Sickness in others often rattles company founders, who fare poorly when there's nothing they can do. Although Gary would have preferred a lighter load during our year of woe, the 12-hour workdays at least offered refuge from his sense of helplessness.

Others take advantage of the flexibility afforded by ownership to modify how they work. One founder I spoke to lost his wife to cancer when his daughter was 8. A single parent of a child with an autoimmune disorder, he reduced his work hours and travel to shepherd her care. With his daughter stable, he remains focused on her well-being. "My business would have grown more had it not been for her illness," he says. "But I make enough to pay the bills."

Sometimes, cutting back is not enough. Drake Sadler is co-founder of the tea company Traditional Medicinals, in Sebastopol, California. When his 13-year-old son, Kai, was rushed to the hospital with a life-threatening strep infection, Drake and his wife, Nioma, planted themselves at the boy's bedside. Kai went into septic shock and was hospitalized for a year. (He is well now and back to being a normal teenager.)

Fortuitously, Drake had recently hired a successor CEO. Instead of the yearlong transition he had anticipated, he made a clean break with day-to-day operations, not returning to the office for seven months. (He is now chief visionary officer and chairman of the board.) "I'm right up there with other entrepreneurs in terms of being a control freak," Drake told me. "With Kai's illness, everything was out of my hands. It was an exercise in letting go."

Such priority-reordering exercises often continue long after the entrepreneur or loved one has healed. After recovering from a severe staph infection that waylaid him for months, Tim Barrett, COO of Barrett Distribution, in Franklin, Massachusetts, devoted more time to his three young children. "A gravestone near my parents' has the guy's company name and logo on it," he said. "That's the last thing in the world I'd want to be remembered for." If illness has an upside, it is the opportunity to remember our true values.

In February, a deadly earthquake struck Christchurch, New Zealand, where Gary was giving a speech. Even before I heard the news on television, he had phoned to let me know he was OK. (His hotel was destroyed. His clothes and money went with it.) So, a close call. And a reminder that fate can take it all away at any time. All we can do is keep building. Our businesses, we hope. Our lives, absolutely.

Meg Cadoux Hirshberg ( writes a regular column about the impact of entrepreneurial businesses on families. She is married to Gary Hirshberg, president and CEO of Stonyfield Yogurt.