Stress generally has negative connotations, but in reality it is not always a bad thing.
Medical experts agree that if one is say, engaged in sport activities or faced with examinations or tests of some sought, then the stress bought on by the situation could be regarded as positive if it helps to raise one's performance and is then dissipated by the body soon after.
If however the stress is prolonged and become continuous unpleasant emotional tensions such as anxiety, anger or depression, then it becomes a risk factor to one's well being.

There is clear scientific proof that the body makes physiological adjustments when stress presents itself. The sympathetic nervous system automatically triggers the body's adrenal glands to produce the hormone adrenaline which when released in the blood increases the heart rate, the blood pressure, the breathing rate, the muscle strength and mental alertness. It also reduces the amount of blood going to the skin and increases the amount to the major organs, such as the heart, the lungs and the kidneys. It is as if the body is given a "Turbo Charge".

This physiological girding of the body to "fight or flight" when confronted with stress, would have been of tremendous benefit to our prehistoric ancestors who were often faced with perhaps having to fight off a saurian lizard or a sabre-toothed tiger, or with further fundamental physical tasks (such as finding food) that were necessary for survival.

Although eminent danger from wild animals is not a major threat today, modern society is fraught with stresses in various formats, which automatically induces physiologically preparation for "fight or flight" in the same way as did our caveman.
For example, as well as struggling with insecure financial status, an individual could be faced with divorce and relationship problems, with meeting dead lines at work, with ongoing arguments with neighbours or the in laws, with jail terms, with worry of job security, with the safety of loved ones in overseas wars, with forced lifestyle changes, to name a few.
In addition, society does not seem to have answers for dealing with soaring rates of civil crime, environmental pollution and the fear of terrorism attacks.

So has the incidence and effect of stress changed since pre-historic times?

Most definitely, but unfortunately for the worse.

You see, the stress encountered by caveman although more fraught with danger, was easier to deal with, because when the threat had passed, there was time enough for him to recuperate and for all physiological effects of stress (including normalising blood pressure) to thus subside. The times of stress were thus isolated incidences that came and went.
Stress associated with modern living on the other hand does not seem to let up. One set of crisis compounded by another seems to be the order of the day. The physiological repercussions of these stresses do not have time to subside and thus become health conditions such as persistent high blood pressure.

The answer?

Simply, we must learn how to relax.
Being able to successfully dissipate stress is a key feature of high blood pressure management.