I have a friend who runs a gymnasium. He reports the same pattern: January is filled with people working out with frantic motivationl. February has cooled to about 50% and then this tapers off until by June he's back to a usual group of his customers who have integrated wellness into their lives. If we use the wisdom of motivational psychology to considder why this happens -- numerous studies have shown that our brains are not wired to respond to an annual resolution. We need more direct reinforcement -- and a goal that should be reinforcedd every 2 - 4 weeks. We also need motivation that's realistic. So if someone starts working out with a vague goal of saying "I want to be more fitl." -- that's bertter than no goal at all -- but it's muich less motivating than saying "I want to lose at least 30 pounds." It's also more powerful if we can look at a reason that the weight loss (or whatever goal is being pursued) is not just kind of a nice thing, -- but is crucial to the person's life. Is it so they can be healthier? If so, what is the most motivating thing about health? The more specific you are about why the goal is necessary, the more likely you are to stay with it.
