Mastery is a progression in the application of skill starting from the very small, and proceeding up the scale to cosmic consequence.
(While "cosmic" may seem hyperbolic, I do not use the term for humorous effect.)
To review, when we are young, and simply exploring the world to assess its variety and the modes we have for interacting with it, clarity of intention is not critical. As we assume the responsibilities of majority, we come into competition for resources with other individuals. In that situation, clarity of intention is critical to success. If we divert our attention, perhaps even for an instant, we can fail. In physical activities, the train of neural synchronization may be lost, and we stumble. In social activities, we relinquish the focus of the community we are attempting to coordinate, providing an opportunity for others to redirect its energies.
In these situations, mastery of the self is essential. One part of self-mastery is strength: power over the self. The other is simplicity, our topic here.
In common usage, simplicity has several meanings. Regarding an individual, it betokens naivete or stupidity. Regarding a life, it implies austerity. Neither applies here. In accomplishing intent, simplicity implies clarity of vision regarding both our goal and the role we expect to play in accomplishing it.
Our federal government is complicated. It reflects two hundred years of practical implementation of a document - the US Constitution - that was never that simple to begin with.
But the first few lines of the Declaration of Independence - those are simple.
The concept of a perfectible government defending the honorable pursuits of its citizens is simple. Once that goal was defined, reality was ordered around it. The men who seriously took charge of guardianship of the notion - the Founding Fathers and their advisors - were able to enumerate the issues, frame them, and reach a workable form of government in a few short months. Of course, they benefited from ten years prior experience of practice and dysfunction under the Confederacy, and several prior decades of philosophical and martial jousting with a remote monarchical superpower. But still, the Founders represented diverse constituencies, with competing interests, and could have descended to intransigent brinkmanship over the issues in front of them. Instead, they compromised where possible, deferred where necessary, and started the great experiment we live in today.