I know your question was how to get in the mood to edit but I'm not exactly sure how to answer that so I'll just say what I do to edit instead.
Write the first draft. Print the first draft. Write something else.
Six weeks later I take that draft and say aloud to myself that I'm going to read "this great book by some up-and-coming-author." And then I read it, realize it's crap, and then sit down with my yellow legal pad and pencil and make notes about everything I want to change (whether it be a badly written sentence, adding a conversation, deleting entire paragraps, etc.). Just seeing the work that needs to be done in order to make it "the great book" I intended it to be is enough motivation for me to begin editing it.
Doubt it'll help, but here's my suggestion: Let the flaws of your work motivate you to turn it into the masterpiece you want it to be.
Good luck and Happy Editing!
P.S. - I forget who said it (maybe Golding?), but it's something like "A great writer is a great rewriter."