Why it's tricky: While health club attendance surges 30 to 50 percent at the start of the year, it's usually back to normal by March, according to data from the International Health, Racquet & Sportsclub Association. It's also hard to incorporate exercise into a busy life: Norcross himself admits that his resolution is to exercise five times a week—usually not a problem, but will be a major challenge when he's traveling.
Make it stick: Research has shown that "self-monitoring" (a clinical term for charting or recording your progress) increases the probability of you keeping your resolution. This is due to the Hawthorne effect, which causes us to try harder when we think someone is keeping an eye on us. Try MyFitnessPal, a tracking app that's a streamlined upgrade of the paper fitness diary.