Weight loss. Already on day 3 and so far I'm very satisfied with my calorie restriction. I want that glorious feeling of feeling your clothes get looser, doubting your progress, but then the next week comes and your clothes feel looser, next week looser, next week, and so on and so forth. That particular feeling will happen mid-January. I've done this before and will do this again.
Other things too, but I don't feel like sharing them.