Stress is the essence of growth (eustress), but constant stress is dangerous to your health (distress). Balancing growth, health and stress is both the definition of stress management and how we achieve our goals.
Stress management can be defined as avoiding unnecessary stressors, dealing with situations as they arise, and recovering from the adrenaline response. In training for a marathon, one would run a little each day, slowly building endurance and speed. Each day one would also recover and rest after the run. It is in recovery from spending energy that our body gains a greater capacity. If you ran until you fell over your first time out, you would not be able to do much of anything for days. If you never run, then your ability to run will remain low. If each day you push yourself just beyond your comfort zone and allow yourself to recover, you will stress yourself to high achievements. It is the same whether you are running, weight lifting, or creating a new habit; a change is a stressor.
Mentally and emotionally it is also important that you take time to recover, rest, and relax to keep yourself at optimal performance. When those unavoidable stressors occur, it is important to both deal with them so they do not continue and to recover so your distress does not continue. 
I encourage many of my clients to find some method of relaxation that works well for them and to make time to practice 3-5 times per day. Just like you could not tango the first time you were asked and you cannot perform any task at gun point that you cannot do in normal circumstances, you will not be able to recover well without practicing relaxation, especially in times when you are not stressed.
The most effective relaxation technique is diaphragmatic breathing. Using your diaphragm to breathe allows oxygenation in the lower lobes of your lungs, releasing more oxygen into your blood stream. In nearly every situation, you are able to focus on and control your breathing; by doing so you will also be able to control your heart rate and other body systems. No one really wants to be told to take a deep breath, but it is often the quickest and easiest way to relax and re-focus. There are numerous effective relaxation techniques. What have you found that you enjoy?
Thank you for the great information!
You are so right about the breathing technique, which is something I learned about 30 years ago when studying karate. Not only has it been something I’ve practiced during exercise, or whenever stressful situations were threatening to put me into a panic-state, one time I believe it might have saved my life, during a medical emergency.
I guess because it sounds so simple, many people disregard it. Or, since it’s been integrated into “complicated” things like meditation and yoga, a lot of people think it must be something difficult to learn or practice. It’s so simple, though, and so effective. You can learn to do it properly in five minutes. Just do it!
You’re Welcome!
Thank you for the testimonial, Dan. It is easy enough for children to learn (I call it “belly breathing”) and can make a powerful difference, especially when one is also able to focus his or her mind.