A smart man knows that he doesn't know everything and surrounds himself with a team of personal advisors who are experts in their field.
We all do that to some extent: we know who to confide in with romantic troubles, which kid to ask for help with the math homework, and where to turn to for juicy gossip.
The personal advisors of a business person could include a lawyer, accountant, local politician, a friend trusted for common sense etc.
It is best if this process is consciously cultivated, so that the potential solution to an arising problem might not be more than a phone call away. One of the most important qualities of leadership is the ability to listen to others.
In the words of R. A. Heinlein: "Always listen to experts. They'll tell you what can't be done, and why. Then do it."