Believe it or not, stress is actually essential for survival. The "fight or flight" response triggered by stressful situations actually help when you're faced with a threatening situation.
But now that humans are no longer being chased by hungry tigers, our stress responses are triggered by more moderate, interpersonal and existential threats. The problem with this is that these challenges tend to be longer-lasting than the tiger, and our stress response systems are constantly in a heightened state of alert. This takes a toll on the mind and body, and, through a process called "allostatic load," can set us up for chronic medical conditions, such as obesity and cardiovascular disease, as well as symptoms of anxiety and depression.
One of the best ways to address stress is to provide people with the tools to cope with it. Cognitive behavioral therapy as well as mindfulness approaches have been shown to improve coping and emotion regulation abilities. So, think of these skills as today's equivalent to fighting off those hungry tigers!
There are many ways to help you manage stress. More problems with stress occur in teens who are overly sensitive to reality.