The devil is in the details. And it is really true.
I had a class once in school that had us start designing a building by designing a detail, a connection that would work well with the building. The dance studio detail never quite made it into the building, however, it got me thinking about the details and how to make them pop.
It is the same in fashion, when planning outfits. If you only wear a simple shirt and pants it may work, but the little accessories are what really makes things pop.
The same is true for any design. It is in the little things, that probably only the designer will notice, that make the work stand out. I know I have designed things over and over again because one line was not in the right place. Nobody would have noticed, and maybe they would have liked it better. However, it is in those little things that really matter.
So, as you are designing, think about those little things, and make sure that they all work together for the greater good of the piece.