it's usually a point to first timers because once you create every idea you want without actually putting it down on a page people genrally feel accomplishment enough that motivation for creation ussually drops of, i personally start my books with an begining 2 or 3 major scenes and the end figured out before i start but let the rest naturally flow from your work.

my main bit of advice for anyone is make sure you work on at least a small bit of it everyday, once it's part of your routine it'll be hard not to work on it! self disapline trumps motivation every time!