In a painting there are active and passive zones. Let me explain that. In my portraits almost always I want to draw the maximum attention to the eyes. So I try to make that zone the most active place in the painting. How? Among others by creating the highest possible articulation of the highlights on the eyes. The mouth is the second in this order of attention. It is clear that the the background is the most passive zone of the portrait. But you will have to pay the same attention to all the parts of the painting. The active as well as the passive. Every part deserves the same attention.
I am painting here the neck and this is not a very active part of the portrait. Nevertheless it has to be well painted. Good colours and good brushwork. And why do I say that? I want to stress that no part of the painting may become a bungled piece of work.
You should seek for the highest dedication to all areas. Passive and active.