A lot of it comes down to the individual really meaning it when they made the resolution and his or her persistence. Do you really want the thing your are resolving to achieve? Are you willing to persist if you hit a few barriers?
Well assuming you do want it and you are willing to persist then the only way you could fail is if you don't have a workable method of achieving your resolution.
Well, I'm sorry to tell you, but that final excuse for failure is gone because a highly workable way exists for you to make your New Year's resolutions come true.
You can read about it online: Targets and Goals
Apply that and your chances of making your resolutions stick will be much improved.