Diamonds start out as rough stones. They must be cut and fashioned to be truly valuable. Editing is like gem cutting: a delicate process by which undesirable material is removed and what remains is polished in order to render a product of real artistic beauty.
Of course, both of these processes require a bit of cutting. Just as gemstones start out as something less desirable, a rough draft must often be shortened through the use of strategic cuts in order to become a viable piece of literature. The genius in editing is to know where to make cuts, what parts are necessary, and how to smooth everything out so the story can be presented in the best possible fashion.
The mind wanders when one is writing. The scene that seemed pertinent is actually peripheral, and perhaps even a distraction from the story being told. It is paramount in editing to be honest with yourself concerning what you want and what you need.
Focus is essential, like the jeweler carefully studying the gem he is cutting. He cannot leave the one piece jutting out, yet there is always the fear that he will cut too much or wind up with a handful of shards. But that is why he works with great care, eschewing both recklessness and frustration.
Editing is a delicate matter, but essential to the fashioning of a satisfying product. Cuts can be painful, but the advantages far exceed any minor inconvenience that is experienced. Slowly and delicately, each page becomes a shining facet of the whole. Once the cutting, grinding and polishing is finished, you hold in your hands a precious gem.