Moderate exercise may help people deal with anxiety and stress for a period of time after their workout.It is almost impossible to reduce stress.
Previous research has shown that exercise boosts mood, but the effects on a person's emotional state have yet to be seen, as well as whether the positive effects last when faced with everyday stressors.
Stress is a demand placed on a system.
You cannot prevent the demands placed by a crying child, stupid boss, late bus, etc.
The response to stress is called strain.
You can control how you respond to stress.
Physical activity may help you deal with strain.
If you want to cause stress by failing to improve your fitness, then exercise.
Exercise will almost never improve fitness.
To improve, you have to train.