Forget vague resolutions.
I've had many years where I come up with 2 or 3 resolutions to keep for the new year. It starts strong, you know, that first week back at work. Usually a few consecutive days of failing at the huge expectation I set for myself is enough motivation to just stop trying. Why did it fail? Maybe I didn't write them down, or they weren't measurable in any way, or it was too large of an assignment to tackle. Most importantly, it failed because they lacked details about how to accomplish them. It's much easier to accomplish a to-do list if the items are black and white, yes or no.
Just make goals instead.
I say forget vague resolutions about X, Y or Z. Start with going from A to B. I'd say 3 or 4 serious goals are enough. But, you have to list out the action items for it, in small, medium and large milestones. It's good to have big goals, but you need to have checkpoints along the way. Think of them as gas stations along the way. A destination on the way to the destination. Checking off the little items makes you realize you are making progress. I think a 'done' list is just as important as a 'to-do' list. If you saw my Creative Mornings talk, you know I'm a big fan of the micro goal concept. Accomplishing small goals keeps you motivated and on track.
Habits are tough SOBs.
Habits can be really sticky, either as a benefit or a detriment. If you are planning on changing a habit for the new year, I'd suggest just try to change one habit at a time. If you try to change your diet, exercise, sleep and TV habits all at once, you will burn through your finite willpower really fast.
Make sure you write your goals down, because if you're like me, your memory sucks. I like to type up a nice looking copy, and post it in my office. It can also help to tell others about your goals, as they can help motivate you with accountability and encouragement. Either post it for yourself to see frequently, or post so many can see.
Time for review.
I like to spend an hour or two at the end of the month to check in on things. What progress have I made? What has prevented me from making progress? If you're stuck, don't panic. Switch it up, and try a different approach. Or break that sticky point into smaller, easier pieces.