Stress occurs when something unexpected and/or harmful that could require quick action takes place. The brain’s reaction is to prime your body for quick movement and in doing so releases a chemical called cortisol. Chronic Stress occurs when you are constantly being stressed for a long period of time, like when you are under a lot of pressure for something like school assignments (which I currently am right now). Chronic Stress can make concentration, focus, decision making, and comprehension hindered. These symptoms can even cause more stress, for example, not being able to focus on an assignment can cause more stress to develop from not being able to complete said assignment. So one wants to minimize stress as much as possible to avoid all these symptoms.
Chronic stress, quite simply, causes a lot of problems, and so you want to avoid it as much as you can. The frustrating part is, a little bit of stress can quickly snowball, because not being able to focus will cause you to fail assignments and then you are more stressed because you failed said assignments. Stress can be good though, as long as it is short term stress, and not chronic stress, because it gives you a boost of energy to get you out of a bad situation.