It's impossible to have a life without stress and worry. Stuff happens, not all of it good, and we need to know how to deal with it.
Before we talk about good stress vs. bad stress, let's look at the definition of stress. The American Institute of Stress states there is no clear definition of stress that is universally accepted but most people agree that stress is a
"physical, mental, or emotional strain or tension" or "a condition or feeling experienced when a person perceives that demands exceed the personal and social resources the individual is able to mobilize." 
In other words, stress occurs when you don't believe you have the ability to cope with or solve the problem at hand.
But this definition doesn't include good stress, the type of stress that drives you to do better, reach further, become more focused. This type of stress is called eustress and happens in our life, every day. Imagine the stress a student feels before taking an important test, the worry that makes him study each night to make sure he does well. Or imagine you are getting ready for your first day at a new job. You are nervous, you are scared, you are worried, but the fear of failure can help you to do your best and put forward extra effort.
We need stress. We need to feel motivated and sometimes we need deadlines or the possibility of a negative outcome to get us moving. Stress can be a positive force. An article in Woman's Day Magazine by Sarah Jio, "7 Ways Stress Can Actually Be Good for You" explains why stress is important and can actually help us:
- Creativity is often borne from frustration and periods of high stress
- Short bursts of stress help boost the immune system
- Stress from moderate exercise helps your body stay physically fit
- When we worry about a decision, we tend to make the decision based on our values
- Worry about your children can help you stay alert and keep your kids safe
- A moderate amount of stress at work can help you perform better
- Short term stress can help you recover from surgery or medical procedures
While these can all help you live a more productive life, it is important to remember they are referring to moderate stress. High levels of stress can lead to high blood pressure, lowered functioning of the immune system, heart disease, higher risk of stroke and can increase your chances to developing anxiety disorders or depression.
So, while you should welcome some stress in your life, you don't want to become overloaded. But there is no right or wrong amount of stress and the amount of stress that becomes "too much" stress is different for each person. Some may thrive on constant challenge while others need a slower, more even paced life. Coping with stress is knowing your limits and learning to manage stress when it becomes overwhelming.
If the stress in your life isn't "good" the following posts can help you find ways to manage:
"7 Ways Stress Can Actually Be Good for You," 2010, March 11, Sara Jio, Woman's Day Magazine
 "Definition of Stress," Date Unknown, Staff Writer, The American Institute of Stress
"Stress-Definition," Merriam-Webster Dictionary