When choosing a goal that is too big, people are often discouraged by unattainable results. Be sure to have a realistic plan for achieving your resolution.
Vague resolutions have less meaning and are easier to break. They also require more mental process when the time comes to execute vs a specific/thought out plan.
Monthly gym memberships and costs from speciality diets can often add up quicker than we expect & are capable of keeping up with financially.
Having support in executing you New Year's resolution is a very important factor in keeping a positive mindset. Online support groups or friends with similar mindsets can really help in cheering you on!