OneTrueThing-- remember part of the essense of NaNoWriMo, is no editing in November.. editting can paralyze our progress and hinder our creativity, because we are constantly trying to figure out the "right words", etc... FOr one month we are to try to let that inner editor writhe in agony as we don't listen to him and just write whatever come to mind, the good, the bad, and the silly...
there were most of last NaNo, I didn't let myself re-read what I had written the day before because I knew that would get my inner editor out and I would not be able to progress... Each day I progressed on my story, but there many not have been total continuity to what I had written the day before... that was ok.. because I was writing something toward my ultimate Novel.
There will be days that you may not like your story... there will be days you will want to ditch the whole thing and start again.... Normally I'd say, ignore those feelings and press on, your feelings may change again in a few days...
As for your case, don't totally ditch yesterday's work... even if it doesn't go into your final product, what you wrote yesterday is helping you propel to your ultimate goal...Those words therefore should count towards your 50,000.. Even if it has nothing to do with your new vision for your book.
Yes, you can start again today with your new genre, since it is only day two you haven't lost much time.. But give yourself credit for the progress you made yesterday... (especially since you were sick!!!)
Well, those are my thoughts on the matter... do with them as you will!