Also, when I wrote I didn't keep it in all one file, just in case I fat-fingered something and lost it all! I wrote in blocks that I retained as separate files, and then copy/pasted into one large document that was just used to count the words to see how I was doing. Here's a screen shot of my NaNoWriMo Evernote folder:

https://dl.dropboxusercontent.com/u/2320179/nanoevernote.jpg

I recommend this method (plus keeping copies in various places) no matter what app you use for writing. Dropbox, Google Drive, etc.