"Aim small, miss small" is a good piece of advice, except that I never want to be thinking about missing.
But why does looking at the whole thing not work?
In our everyday life we are accustomed to walking around and recognising things by their shape, colour, movement and context.
We are naturally accustomed to looking for and looking at shapes.
The part of our mind that is good at aiming is the subconscious,which naturally tries to give us what we expect by having us shoot where we are looking.
If we find ourselves shooting at some part of the outline and so tending to miss or just catch an edge, it is almost certain proof that we have relaxed our attention and fallen back on looking at the whole object.
It is also why it is a commonplace experience that folks who are not known for their accuracy will actually manage to inadvertently concentrate so many of their shots in such a narrow perimeter zone.
In fact we will find in formal target shooting that when we look at the whole of a spot or centre circle that we will tend to shoot arcs around the perimeter of that spot.
It is also one of the reasons why so many club shooters put so many arrows in the white ring on the Prince's colours. Apart from being the largest area, it is also what they tend to be lookingSo it is reasonable that we should learn to look only at the smallest possible exact mark that we wish to and will expect to hit.
For myself I can say in all honestly that I rarely miss. It is just that I am not always looking where I should, or with the necessary level of commitment.