Stress is your body's way of responding to any kind of demand or threat. That demand or threat once upon a time was things like lions, tigers, or bears. Now, our stresses are slightly more tame: a looming deadline, a botched sales call, or a tricky office relationship.
When you sense danger - whether real or imagined - the body kicks its defense mechanism into gear with the fight or flight response in an effort to save your life. Your body either wants to flee from the dangerous beast that's trying to eat you (or your lunch that's in the office fridge), or stand its ground and fight.
Stress: Good vs. Bad