Atrophy (noun): degeneration, decline, or decrease, as from disuse; wasting away
I've seen the effects of atrophy up close. In athletic training we would work with athletes returning from broken bones and periods of immobility who had to work to rebuild muscle tissue. In ministry I have witnessed people who have neglected important disciplines long enough to forget how to do what used to be instinct. Both areas represent an important fact for all of us: if you don't use something you will lose it. It may not be gone forever, but it will take some work to get back to a comparable state. This is a life principle that applies to physical activity, spiritual disciplines, relationships, and overall positive life habits.
If we want to avoid a personal regression we can't ignore the practices that brought us to a place of growth. Rest when it's necessary, but be consistent in doing the things that bring good health to all parts of your life. Nothing healthy was ever achieved by wasting away.