In ten months and four days one of you will wake up as Mr. or Mrs. President. After the fabulous fun of post-inaugural balls (I wonder if I'll get an invitation after this letter), you will walk into the Oval Office on Saturday, January 22, and launch into your first 90 days in office, during which you will want to deliver on as many of your promises as possible. But instead of shadowboxing with hypothetical futures on a debate stage, you're going to be up against cold, hard reality.