I think New Years resolutions are wonderful to make, but people become rather disenchanted when they make too many/unrealistic ones. "I'm going to become an astronaut and land on Mars!" for example, might be a little far-fetched. The key to a good resolution, I think, is small, achievable goals - and maybe a few big, exciting ones (and of course, small doesn't necessarily mean boring). Achievements have long been shown to immensely improve people's self esteem and happiness.
I actually haven't really made a habit of doing them, but I think I'll start this year. They seem fun to do, if nothing else!