When you set that lofty New Year’s resolution at the stroke of 2017 , March probably looked a lot different in your head: You’d be fitter, slimmer, happier, healthier. “People make their resolutions in a ‘bubble’ of overindulgence,” says Michelle Segar, Ph.D., a motivation scientist and author of No Sweat: How the Simple Science of Motivation Can Bring You a Lifetime of Fitness .