The enso is an ancient Japanese symbol representing the strive for perfection.
What is extremely symbolic about it is that ensos, which are painted with paintbrushes on paper, are never the same. The intention of the artist is always to create the perfect circle, yet he never achieves it. Each circle is thus perfectly imperfect in its own right.
To me, it represents what many of us are doing here. As idealists (I think most of us are) we aim for something amazing, knowing well we might not achieve perfection but making the efforts and creating something beautiful none the less.