The real hard part comes after the initial novelty and the quick progress fade away: Staying motivated to do regular workouts without getting faster or lifting more weights every week.

This also applies to healthy eating habits. Once you've reached your target weight and the novelty wears off, it's much harder to eat clean. Personally, I like pizza once per week, usually on Friday, as celebration and reward that it's finally weekend.

For exercise it boils down to discipline. At least for me. Plus, I feel really, really bad and get in a terrible mood if I cannot physically exert myself every day.