"One of two choices?" you ask. "Isn't there a third choice? Staying the same...?"
Nope; there are only two choices. Nothing in between. Ask any business professional or athlete -- you're either growing or shrinking, improving or going downhill. There's no such thing as maintaining. (Why would we want to maintain, anyway, when we can always choose to improve?)
When I tell you that you get to choose, that doesn't mean that your choice needs to be a conscious one. You're making your choice all day long, every day, whether you're thinking about it or not -- what you eat, how physically active you are, how often you have your spine adjusted, how much clear water you drink, how you relax, how much sleep you get, whether or not you engage in a spiritual practice, how much you laugh, and many other choices.
Think back to the choices you made yesterday. Taken as a whole, in which direction did those choices steer you...toward becoming more healthy, or less. What choices will make today...this week...the rest of the year...the rest of your life?