Design is harmony. It's not the substantial harmony "being" among the parts of an object, but the dynamic harmony "becoming" between the subject and the object. Good design should not be perfect. The perfect is not in need of any other external existence. It refuses foreign bodies. The design must let others in and permeate into; it should have insufficiency, the void.
A perfect house in itself does not allow its residents to step in. Instead, it should be something imperfect that they can get inside and harmonized with; the house lives in the residents, and the residents in the house. -- JuneKim
ps. This applies to architecture, UI design, computer programming, whatever design is related to.