Stress doesn't just motivate us to get things done. Short bouts of it may actually boost the immune system and protect against one type of cancer, according to researchers at the Stanford University School of Medicine, who were able to show the effects using stressed out laboratory mice.

Chronic, relentless stress can tax the immune system, increasing your chance of getting sick. But occasional angst may enhance anti-tumor activity, according to the study, published in the journal Brain, Behavior, and Immunity.

"Evolutionarily, it makes sense," said study author Firdaus Dhabhar, a member of Stanford's Cancer Center. "In nature, stress and immune activity are typically coupled. It's like a lion chasing and wounding a gazelle. Nature taps into this stress response to give a boost to the immune system in the face of danger."

In the Stone Age, life was arguably more stressful, said Dr. William Meller, who specializes in evolutionary medicine and was not involved with the Stanford study.

"Every day was a struggle for food, safety, shelter, fighting off disease and predators," said Meller, who was feeling admittedly cranky when I contacted him. "They didn't relieve this by meditating. They sharpened their knives, hunted for food and built shelters. One of the reasons we think we have so much stress today is because people spend so much time doing useless things to 'alleviate' it rather than getting things done."

Meller concedes that we all have different abilities to handle stress. Some of us live with huge responsibilities and workloads while others get stressed by getting out of bed in the morning.

But instead of adding another task to your list, such as yoga or exercise, you can reduce your stress by getting your work done, he said.

"If you have a writing assignment, it doesn't do you a bit of good to go to a yoga class. You sit down and do the writing and the 'stress' miraculously goes away," he said.

There is room for disagreement. Many practitioners vouch for yoga or meditation, saying they can help us sleep and improve focus. There's research showing that exercise can increase concentration, which can also help you get your work done.