​Human bodies are genetically programmed to produce a "fight or flight" response in frightening or threatening situations. This adrenaline rush is great to have in emergencies. It focuses all your energy on the crisis, makes you extremely alert, and gives you strength to do what's needed with maximum efficiency. After the rush, though, your body needs time to relax and refuel, if it's going to function well in the long run.

A certain amount of stress is normal. Minor annoyances and challenging tasks have to be dealt with every day. Losses and unwanted changes happen to everyone. And, of course, we wouldn't want to live our whole lives avoiding risks, never trying anything new.

But, unlike the distant ancestors from whom the fight-or-flight stress response probably evolved, most of us today aren't facing one life-threatening emergency after another. Mustering the strength to fight a saber-toothed tiger just isn't necessary anymore. The central nervous system, though, can't distinguish one kind of crisis from another. All it knows are the basic feelings of rage (fight) or fear (flight). Arguing with your boss, swerving to avoid a freeway accident, hearing a loud noise, or walking up to a podium, all have the potential to get your heart and breath racing, make your muscles tense up, and get your palms sweating. A major crisis or emergency can create one stressful moment after another, exhausting your body as it tries to keep generating the hyper-alert, hyper-energetic stress response.

An interesting thing about humans is that our bodies actually do recover pretty well from the stress response that occurs in moments of crisis. But stress that doesn’t let up, even if it’s at a fairly low level, really takes a toll. That’s why ongoing issues such as family problems and job burnout can have a big effect, over time, on physical and mental health.​

​Positive feelings can trigger stress, too, especially if they’re about major life changes. Getting a new job or getting married are high on the list of events that raise stress for most people. It could be that the fight-or-flight response comes into play simply because you're about to encounter something unknown.  Just like rage and fear, excitement can be hard on the mind on body, if it's too intense or lasts too long.  One definition of stress is that it's what happens when an organism (like your body) receives more stimulation, pleasant or painful, than it can handle.​

What Causes Stress?​

Often, the way you think or feel about a situation can affect your stress level. Even a small problem can seem unmanageable if it reminds you of something traumatic or truly overwhelming that happened to you in the past. If you catastrophize a problem; stay focused on guilt, blame, or "shoulds"; or think only in black and white terms; it will be harder to relax and come up with a creative solution. The fact that your thinking patterns influence stress is actually good news. It means you can learn ways to think that will help you relax and feel better. In this way, your mind can make your body healthier.

Your body can help your mind feel better, too. The opposite of the stress response is the relaxation response. When you use relaxation techniques to slow down your heart and breath rate, your mind takes a cue from your relaxed body and becomes convinced that everything is going to be okay.

The trick is not to create a problem-free, stress-free life, but to manage stress, by doing whatever you realistically can to keep problems in perspective, pace yourself, and make sure you have time for the relaxing and refueling that your mind and body need. Depending on what’s causing stress for you, it may be necessary to change your situation, find a more positive way to think about it, get support from other people, or use relaxation techniques to help yourself feel calmer.