Breaking up the symmetry
A balanced composition will feel and look right, it is asthetically pleasing. Elements may be the counter point or the focal point and attract the eye, no one area will distract or draw the eye so much as to distract from other areas of the composition.
In this we are in the process arranging both positive elements and negative space...when this is achieved the whole becomes greater than the sum of its parts.
When this is realised and understood we can unbalance the composition to create tension in the sheme...