Stress has been linked to dozens of health conditions, including the "big ones," such as heart disease or cancer. Stress has also been linked (no surprise) to feeling irritable and not sleeping well. By focusing on stress, you can improve your quality of life right now while improving your long-term health and life expectancy too. That's a pretty good deal.
You can destress through a wide range of stress reduction techniques. My personal favorite is called the "relaxation response." This is a scientifically proven breathing technique that will help train your body not to respond to the stressful events in your life.
My other more long-term relaxation technique is meditation. By learning how to meditate, you not only calm your body, but you begin to train your mind. This is great for mental fitness, concentration and (of course) relaxation.