Depends on the level of distress. It's not assumed to be comfortable to exercise as you are putting your body below pressure to achieve change and growth. But you are tired to the point of not being capable to work correctly, you are either struggling too strong or may want to find an MD to assess you. Also if you are inclined to any kind heart disorder let someone know where you are when exercising or better still let them be at your front at all times.
For one teens get addicted mostly through peer-pressure and two the brain becomes confused with whats wrong and whats right once you start and can't quit.
