The exact counterpart of stress is of course relaxation. There are so many ways to reach a level of relaxation so that stress isn't a bothersome issue in our lives.
In the daily humdrum business of our existence the stress response occurs naturally. During ancient times stress existed in a miniscule fashion of course compared to today's situation. It also had very different reasons. People were hassled and stressed mainly due to life threatening situations by predators, etc. In today's day and age stress is triggered through everyday situations at work, at school, at home, in relationships, or there could be a competitive situation in a game or even living up to the Joneses could trigger stress.