The ability to start something you cannot finish is no measure of capability.
1. Mental calmness, composure, and evenness of temper, esp. in a difficult situation.
As a CEO, you have authority over the entire company (though again not true control over every individual’s free actions), but you need to be worried about all the users and customers, competitors, large-scale industry trends, macroeconomic forces, regulators and governments, the press, etc. Thus, being a CEO requires developing extreme mental equanimity in the face of feeling nearly totally powerless - and still being able to make effective decisions using the limited resources you can control.