It is a feeling of nervousness or worry. It's what helps us to not make the same mistake twice or to avoid or be careful when performing a risky or dangerous task. When people have a high level of anxiety most of the time for no apparent reason, then it can be a problem. Most of us have more anxiety than we realize. One of the worst prices of technology is increasing levels of stress.
Any city is a large collection of potential stressors.
You have the mass media, mass transportation, vast technological innovations, and intense inter-personal stimulation. And you always seem to have a deadline. We live in a deadline-oriented society. An increased level of stress causes d ecreased learning ability, inhibits the immune system and increases homocysteine and bad cholesterol levels. Chronic stress actually ages the brain.