Many factors cause stress. For example, illness, being late to work, traffic, etc., but the most important factor is our attitude, our attitude towards the events that happen around us.
There is no single level of stress that is optimal for all people.
Each of us are unique creatures with special needs. Therefore, what is sad for one person, may be happy for another. Even when we agree on the distressing nature of certain events, we probably differ in our physiological and psychological responses to that event.
A person who is fascinated by negotiation and dispute resolution and job mobility, if he has a monotonous job without movement, he will be under pressure and stress. While a person who is interested in stable conditions, when he is placed in a job where his duties are highly varied, he is likely to feel stressed.
Before being exposed to annoying changes, what our personal stressors are and how much we tolerate them depends on our lifestyle and age.