system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the stress on your heart from stress bad while the stress on your heart from exercise good?

Both stress and exercise make your heart work harder, increase blood pressure, release adrenal hormones, etc.

But when under constant stress, its bad for your circulatory system.

When constantly working out and causing those same effects, its results in a stronger cardiovascular system and heart?

Why?
gpt
There's actually nothing wrong with stress. Yes it makes your heart work harder, increases blood pressure, reduces blood flow to non vital (to this situation) organs etc. But all of these things are really useful when you are in a fight or flight type situation. When you are doing exercise, these things are all beneficial to the situation. If you are being chased by a tiger, these are all good things. That's why stress exists.

Stress is only a problem in current society because people are stressed about non-physical danger. Stress is a response to an immediate physical danger, in an attempt to help you survive. If you are stressed about something like an exam, all these cardiovascular changes are inappropriate. Your heart is working harder, but you don't need to deliver more oxygen anywhere. Digestion is stopped because it is non-essential but you may still be eating (as you are not in imminent danger). 

People in high stress jobs can also remain in a stressed state for very long periods of time. The stress response is only useful in the short term. Shutting down things like your gastrointestinal system for long periods can cause bowel problems and stomach ulcers. Temporary increases in blood pressure are useful for exercise but inappropriate long term, increasing the risk of heart attacks and strokes. Even when you are 'constantly working out', this is not really constant. Usually an hour or so a day. You can be stressed all day everyday for months or years.