While many of the other methods of dealing with stress, or better yet, eliminating stressors, are great ideas, I have found that I was crreating some of those stressors myself because of the way I percieved events at work, not the events themselves.
For instance, when I first started as an instructor I would take it very personally when a student performed poorly in my class, to the point where it caused a lot of stress and I know I laid awake nights thinking of it. I was creating stress in my life about things that are not within my control. I now ask myself, did I offer all the help I could? Did I do everything I could to ensure the student's success? If I can answer myself honestly, with a yes, and the students failed to take advantage of what was offered to him because of a lack of motivation on his part, or if failed to grasp a concept after explaining or demostraating the concept using every learning style method I could come up with, then I am not at fault, and should not personally suffer stress because of something I am not in control of.
Other things I can control, I manage, things I can not control, I simply dismiss. I will not allow myself to loose sleep or become ill because of things that are not within my control.