In 2009, Newsweek asked, "Who Says Stress Is Bad For You?" http://www.thedailybeast.com/newswee...d-for-you.html
Most already know not all stress is bad.

Sure, stress can be bad for you, especially if you react to it with anger or depression or by downing five glasses of Scotch. But what's often overlooked is a common-sense counterpoint: in some circumstances, it can be good for you, too. It's right there in basic-psychology textbooks. As Spencer Rathus puts it in "Psychology: Concepts and Connections," "some stress is healthy and necessary to keep us alert and occupied." Yet that's not the theme that's been coming out of science for the past few years. "The public has gotten such a uniform message that stress is always harmful," says Janet DiPietro, a developmental psychologist at Johns Hopkins University. "And that's too bad, because most people do their best under mild to moderate stress."

The author:

When I started asking researchers about "good stress," many of them said it essentially didn't exist. "We never tell people stress is good for them," one said. Another allowed that it might be, but only in small ways, in the short term, in rats. What about people who thrive on stress, I asked—people who become policemen or ER docs or air-traffic controllers because they like seeking out chaos and putting things back in order? Aren't they using stress to their advantage? No, the researchers said, those people are unhealthy. "This business of people saying they 'thrive on stress'? It's nuts," Bruce Rabin, a distinguished psychoneuroimmunologist, pathologist and psychiatrist at the University of Pittsburgh School of Medicine, told me. Some adults who seek out stress and believe they flourish under it may have been abused as children or permanently affected in the womb after exposure to high levels of adrenaline and cortisol, he said. Even if they weren't, he added, they're "trying to satisfy" some psychological need. Was he calling this a pathological state, I asked—saying that people who feel they perform best under pressure actually have a disease? He thought for a minute, and then: "You can absolutely say that. Yes, you can say that."

The conclusion:

This is the problem with all stress-management tactics: you have to want them to succeed and be willing to throw yourself into them, or they'll fail. If you force yourself to do them, you'll just stress yourself out more. This is why exercise relieves stress for some people and makes others miserable. It's also why Sapolsky says he's "totally frazzled" but doesn't bother with meditation: "If I had to do that for 30 minutes a day," he says, "I'm pretty sure I'd have a stroke."

For all of the science's shortfalls, there's animal research that suggests why something that should lower stress can actually cause stress if it's done in the wrong spirit. In a classic study, scientists put two rats in a cage, each of them locked in a running wheel. The first rat could exercise whenever he liked. The second was yoked to the first, forced to run when his counterpart did. Exercise, like meditation, usually tamps down stress and encourages neuron growth, and indeed, the first rat's brain bloomed with new cells. The second rat, however, lost brain cells. He was doing something that should have been good for his brain, but he lacked one crucial factor: control. He could not determine his own "workout" schedule, so he didn't perceive it as exercise. Instead, he experienced it as a literal rat race.

This experiment brings up a troubling point about stress. Psychologists have known for years that one of the biggest factors in how we process stressful events is how much control we have over our lives. As a rule, if we feel we're in control, we cope. If we don't, we collapse. And no amount of meditation or reframing our thinking can change certain facts of our lives. With the market languishing and jobs hemorrhaging and the world going to hell, too many of us probably feel like that rat in the second wheel: it's hard to convince ourselves we're in control of anything.

But stress science even provides a little hope here, if we go back to Selye. He first published his ideas during the Great Depression—a time of stress if ever there was one, and a time in which survival demanded creativity. That Depression ended. Now we're entering what may be a new one, and we'll need more creative thinking to get out of it. We're going to have to figure out what parts of our future we can control, and we'll need to engage with them thoughtfully. Fortunately, we have the kind of brain that permits that. Sure, it will be stressful. Maybe that isn't a bad thing.

Dr. Liz Hale has a different view:

Have you noticed the mixed messages in the media about stress?

A national news magazine recently put an eye-catching title on their cover, “Stress Can Be Good for You.” How is it after years of warnings about the damage stress can do to your heart, your immune system and your psyche, we are now hearing that stress can be good for you? Dr. Liz Hale, our own Clinical Psychologist says, don’t believe everything you read.

Stress is indeed hard on everything just mentioned – it’s also likely hard on the brain. New research in animals reveals stress can shrink brain tissue and make our neurons less effective at communicating with each other. Scientists are also investigating the genetic link with stress. How genes may affect the way our brains process stress and depression and how stress effects pregnancy.

Q: What is the stress mechanism exactly…how does it all occur and what exactly happens to our body and mind?

Here is a list for you to use: Might be impressive to have it scroll thru while I mention only a few specifically…..?

• Increased heart rate
• Increased blood pressure
• Blood vessel constriction
• Heart rhythm disturbances
• Increased stomach acid
• Increased muscle tension
• Increased cholesterol
• Increased blood sugar
• Short shallow breathing
• Abnormality in immune function
• Fluid retention
• Anxiety
• Depression
• Anger, rage or hostility
• Irritability
• Decreased concentration

Hale then discusses some of the problems related to stress and provides some steps to reduce stress. I found her article well worth reading.

As noted, the line between helpful stress and bad stress has no bright line. Undoubtedly, at least for me, learning how to manage stress is essential to a healthier life.

Dr. Grohol has a lot of good information about stress here: Stress Management