I don't believe in New Year's Resolutions because I don't think they work. Instead, I would rather set goals for things I want to accomplish. I think it's much less pressure that way and it seems doable.
Whenever I set resolutions in the past, they were always about weight loss and they never worked. I would be like others... workout for a few weeks and stop going for a while after that. I would change my diet briefly and go right back to the junk food within days.