According to a report to be published in the upcoming issue of Psychological Bulletin, people who attend church regularly - or at least have internalized a strong commitment to religious values - will have an easier time keeping their New Year's resolutions.
It's not just that it takes self-control to sit through religious services. Even accounting for selection bias, according to this blog post in the New York Times, people who attend services end up with more self-control, even if they didn't start with much.
Further, people with strong religious convictions are better at resisting temptation (if that's what one wants to do with it).
But what's most intriguing, from a Humanistic perspective, is the way in which the study does - and doesn't - correlate "religion" and "spirituality."