The hardest part of doing anything is often showing up. And when it comes to exercise, it's easy to think up a billion and one reasons to put gym time on the back burner. But a simple way to stay committed and turn workouts into a no-brainer habit is to schedule them in. Research suggests it can take as little as 18 days (but an average of 66 days for most!) to form a new habit, and penciling in gym sessions ahead of time (like an important meeting or a friend's birthday) is just one way to get that butt into gear -- for the long-haul.