In Zen art, an ensō is a circle hand-drawn in one or two uninhibited brushstrokes to express the Zen mind, which is associated with enlightenment, emptiness, freedom, and the state of no-mind.

The ensō symbolizes absolute enlightenment.

The circle may be open or closed. In the former case, the circle is incomplete, allowing for movement and development and the perfection of all things. The space inside the circle may represent the state of the realization of emptiness or no-mind.

I feel that a solid complete circle would represent that I am totally one.  

That no circle would represent total separation from one.

The ensō used on this site represents my current state. 

Periods when I am fully one, periods when I am dreaming, and fluctuations between the two.

By not being a completed circle representing human, still living in this world.