A New Year's resolution is a promise you make to yourself to start doing something good or stop doing something bad on the first day of the year. A firm decision made on New Year's Eve or New Year's Day to do or refrain from doing something over the course of the next year. To achieve weight loss as a New Year's resolution, consistency and making small changes are key, for example, if you're trying to lose weight and decide to become a vegetarian to help you achieve it, you'll want to consider whether this is going to be a drastic change for you. One of the biggest mistakes people make at the beginning of the year is that they establish a New Year's resolution that is too difficult or too big to keep.
American definition and synonyms of New Year's resolution from Macmillan Education online English dictionary. New Year's resolution is a kind of grand, glorified, long-term goal that people, for social reasons, tend to start on the first day of the calendar year.