Stealing the title from Jocko:
When I was an engineer most of my tasks were defined. It was easy to work on those tasks as long as I followed the process that someone else had developed and I had less stress due to ambiguity. Now that I am a manager my tasks are less defined and it is easy to shoot from the hip anytime I have a task to complete and I have more stress from ambiguity.
When I define processes and am disciplined to follow the processes my stress is reduced.