This can be difficult because to worry is easy. Worry about yesterday or tomorrow adds to stress. Positive thinking takes practice. We can change our physical state with our thoughts. Learn to use a relaxation technique.
Conscious relaxation reverses the physical stress response.
If there is a benefit to illness, it is that we can learn what is important in life and what isn't. Recognize what has meaning for you in your life. Establish clear and realistic goals for your personal and professional lives. Manage time, don't let it manage you. Pace your activity.