Happy New Year! Don't make a resolution. Instead, take advantage of the market for them.
Right now, gym memberships, diet food sales and clothing store clearances are all around you. This is the perfect opportunity to try out a workout class you didn't have the coin or nerve for because the gym thinks you've made a resolution, when really, you're making a smart shopping decision. Just make sure you fully understand the trial terms and haven't signed up to anything. You might find something you love, or something you love to hate!
Get some cute gym clothes. I tend to seek out yoga pants with pockets, but now all sorts of places make all types of clothes from moisture wicking pants to harem style gym shorts. I have no idea why you'd want the latter, but they are out there. And since stores are prepping for spring, get them on the cheap!
Sometimes, healthy food is expensive. Treat yourself to some sort of food you'd like to try, more than likely there's a coupon or discount for it online somewhere or in a circular.
Mostly, realize you're the same person you were on December 31st, just today you're probably hungover and you'll be the same person next December 31st if you choose to be. There's no list, no wish or promise that can change that. If you fail at something, be content that you went out to do it or try it, and if it means something to you, fail and then get up to finish it.