Know the difference between what you can and cannot change, and change those you can. Accept the rest. Most situations can be viewed from several different angles. It is possible to give most stressful situations a positive name. Shift from worrying to problem solving.
Problem solving is the active attempt to find solutions to problems.
At times, it may be better to try no solutions than to apply wrong solutions. Pat yourself on the back. Set realistic goals and expectations daily. Allow for human error. If you seriously want to ease stress, the key lies in determining the source.