Why do we need to relax? 

High levels of stress, worry, anger, fear are bad for our mental and physical health.  Examples of the most significant problems are:

Heart disease - Stress can directly increase heart rate and blood flow, and causes the release of cholesterol and triglycerides into the blood stream. It's also possible that stress is related to other problems -- an increased likelihood of smoking or obesity , excessive drinking which indirectly increase the heart risks.

Asthma. Many studies have shown that stress can worsen asthma. Some evidence suggests that a parent's chronic stress might even increase the risk of developing asthma in their children. One study looked at how parental stress affected the asthma rates of young children who were also exposed to air pollution or whose mothers smoked during pregnancy. The kids with stressed out parents had a substantially higher risk of developing asthma.

Obesity. Excess fat in the belly seems to pose greater health risks than fat on the legs or hips -- and unfortunately, that's just where people with high stress seem to store it. "Stress causes higher levels of the hormone cortisol," says Winner, "and that seems to increase the amount of fat that's deposited in the abdomen."

Diabetes. Stress can worsen diabetes in two ways. First, it increases the likelihood of bad behaviors, such as unhealthy eating and excessive drinking. Second, stress seems to raise the glucose levels of people with type 2 diabetes directly.

Headaches. Stress is considered one of the most common triggers for headaches -- not just tension

Depression and anxiety.   It's probably no surprise that chronic stress is connected with higher rates of depression and anxiety. One survey of recent studies found that people who had stress related to their jobs -- like demanding work with few rewards -- had an 80% higher risk of developing depression within a few years than people with lower stress.

Gastrointestinal problems. Stress is also a common factor in many other GI conditions, such as chronic heartburn and irritable bowel syndrome (IBS),

Alzheimer's disease. One animal study found that stress might worsen Alzheimer's disease, causing its brain lesions to form more quickly. Some researchers speculate that reducing stress has the potential to slow down the progression of the disease.

Accelerated aging. There's actually evidence that stress can affect how you age. One study compared the DNA of mothers who were under high stress -- they were caring for a chronically ill child -- with women who were not. Researchers found that a particular region of the chromosomes showed the effects of accelerated aging. Stress seemed to accelerate aging about 9 to 17 additional years.

How can a feeling have all this negative impact on our body?
Stress isn't only a feeling in your body or a way of thinking that is unpleasant.  It's a built-in physiologic response to a threat.  When you're stressed, your body responds. Your blood vessels constrict. Your blood pressure and pulse rise. You breathe faster. Your bloodstream is flooded with hormones such as cortisol and adrenaline.  Your sympathetic neverous system is activated.  This physiological process is useful when under physical threat but in our modern lives fighting or fleeing won’t usually resolve the problems and therefore the feelings don’t always dissipate easily.

Solution : Learning to relax
While the number of health problems related to stress might be alarming, don't despair.   Learning to relax deeply, thereby activating our “parasympathetic nervous system” can hugely reduce the stress you experience.

You life may be extremely busy and you find yourself thrust into highly stressful situations on a regular basis and you cannot remove the stressful things in your life but you can learn to use relaxation to change how you respond to them thereby reducing the symptoms of stress and its negative long term effects.