NaNoWriMo is a challenge. There's no way of getting away from that. 50,000 words in a month looks like the north face of the Eiger right now. If it were an athletics event, I'd have been in training for months now, busy writing so many words a minute. Yet here with a few days to go and the most I've written in the past month is this... I don't give myself much of a chance, yet I'm still up for the challenge.
They say that preparation is everything when it comes to writing. Some writers I know plan their stories to the nth degree, whilst others just write. Which way you do it is down to you. What makes you happy certainly works here. Whether your mind must be happy is a moot point. I find writing easier when I'm in a slump. The emotions let my writing hit a certain style that I kind of like.
Having a story or the idea of a story is something you need. You don't get very far without a bare bones idea. You can then flesh the bones out as much as you want. Some prefer to have a fully worked idea before starting. All the locations, characters, and plots finally tuned. I prefer to go halfway. I've the overall plot in my head, or even if I'm careful, written down. I know the characters I'm going to have, or at least the main ones. The locations are there. Some of the subplots are together but not all.
I quite like the spontaneity of writing though. To this end I like to be able to pull some ideas together whilst writing. Ideas come to me that I might try and include as they sound good at the time. Editing will solve that problem won't it ?
I'm going into NaNo with a promising idea. What it'll turn out like I've no idea. In my mind it'll be a best selling story. Reality, on past record, will prove otherwise. Still it'll be fun, won't it?