Not cathe here.
Over the years I have read a bunch of books on exercise. All of them that give work out programs, even running books, throw in a rest day.
The problem is that some weeks, you feel energized and can't wait to get moving and get those endorphins going, and the thought of sitting around all day without doing something is very frustrating. Sort of like not dancing when you hear that catchy tune you have always liked.
One way to compromise is to vary what you do. On what should be a rest day, if you're exploding with energy, do something but make it different. If you never run, throw in a run, or a combined run/walk (walk a block, run a block, walk a block, run a block). If you never walk, go walking, take one or two pound dumbbells, and do biceps curls, side lat raises, front raises, delt squeezes, kickboxing punches (jabs, hooks, uppercuts) while you're walking (if this embarrasses you wear a hat with a big visor and sunglasses). Do a bike ride. Try skipping rope (it beats me up totally).
The virtue of doing something different in a non-rigorous manner is you use your muscles in a different way (i.e. cross-training). But go slow so you don't injure yourself by overdoing.
