Cindy Tysinger GSATi (No. 170 on the Inc. 500)

When cash got tight, Tysinger's son invested $250,000 in her company. "That was the hardest thing ever, going to my son to borrow money," she says. "Humbling yourself to that point is difficult. I just want to take care of everybody, you know?" Around that time, anxiety made it hard to sleep and blunted her appetite. She lost 30 pounds. Her family tried to make her take breaks by unplugging the home Internet connection.

What she's learned: Get outside. "I love to walk," she says. "Even if I was thinking about things I needed to do, I was in fresh air, nature."

Toby Thomas EnSite Solutions (No. 188)

Thomas started his company with two partners who, he claims, did not do their share of the workload. Six months later, he bought them out. "That was a very scary point," he recalls. "When you go into a business with partners, you're spreading the risk out. But when you suddenly don't have that support system, it's like you're in a black hole."

What he's learned: Find a CEO support group. Thomas is a member of Entrepreneurs' Organization, a global nonprofit founders' network. "It's very Skull and Bones," he says. "People completely open up. You have to sign a constitution that says you can't even tell your wife about what you talk about."

Grier Allen BoomTown (No. 433)

A publicly traded company bought Allen's main competitor and rebranded its entire business around that company's technology. Allen tried to stay calm and focus on the market segment where BoomTown was strongest, a strategy that later paid off. But the stress was getting to him and shortening his temper.

What he's learned: Jog it off. "Running releases a lot of stress," he says. "It clears my mind and lets me detach from the digital world for a little while. If I don't get out and run at least twice or three times a week, I just start feeling crazy."

Yisroel Bruce Krinsky Renegade Furniture Group (No. 127)

Krinsky's first venture, at 21, was importing dried-fruit energy bars from South Africa. He got the product into 200 stores, but there were no repeat orders, and the company flopped. "It was heartbreaking," he says. "Every time I went to check on the product with a big smile on my face, it was all still sitting on the shelf. I was really upset, and I felt kind of like a loser."

What he's learned: Play the long game. "If you can think of any problem you have today, picture your reaction in seven years," he suggests. "Will it be affecting you then?"

Andrew Laffoon Mixbook (No. 177)

Mixbook nearly ran out of cash three times before getting venture capital funding. "We were pitching VCs day in and day out," Laffoon recalls. "We got a lot of soft nos. I was sick to my stomach for weeks."

What he's learned: Remember that you're not the business. "If your identity is all wrapped up in this company you've built," says Laffoon, "when someone rejects it, they're rejecting you."