I write for me. But editing that way would be too selfish.
At night, when I pour over whatever I penned earlier in the day, I try to wrest myself from my characters' heads and my own mind and place myself in the heads of three people: my dad, my closest friend from elementary school, and my agent. Each person is very different. And, if I can please these imagined readers, I feel good about continuing my story.
My father is the critic. A sixty-six-year-old, soon-to-be retired accountant, my father scrutinizes stories like a balance sheet, searching for mistakes and plot failings. He wants to point out that something didn't make sense or that a character's actions were "unbelievable." He refuses to allow well-crafted sentences to seduce him into an easy suspension of disbelief. Reading with my father in mind forces me to constantly ask myself whether or not I've done enough work to make my characters' actions natural. If my fiction doesn't feel truthful, my dad's voice will accuse me of lying with all the venom of a parent thinking of a punishment for breaking curfew. I'll need to go back to the drawing board.
My closest friend from elementary school is probably the person in this world most similar to me. She reads often. She likes stories. She enjoyes being entertained. However, she's a super busy working mother with a ton of responsibility. She doesn't have time for tales that don't keep the pages turning. If my story is not exciting and the characters are not compelling, she's going to put it down--even though it was written by her best friend. There are just too many other pressing things demanding her attention. When I'm editing, I imagine her reading my book after putting the children to sleep. Does she place it on the nightstand because she's tired or can she not help herself even though she knows her kids will wake up early the next morning and she'll have to get them all ready for camp before heading to the office? If I can still have her imagined attention, then I'm telling an exciting story.
My agent is the seasoned professional. She's read so many thrillers that few plots seem original and few stories aren't predictable. She is my barometer for genre aficionados. If I can surprise her with a twist--or at least delay the inevitable guessing until the third act--then I may have something that will please serious mystery readers.
If, in my head, I've kept these three people interested in my story, then I've done a good job writing something that I can take pride in. If not, I need to write something better the next day when I'm back to being me.