A nutritional counselor once told me to never go more than two days without exercising. She emphasized that it didn't have to be the full-on workout gear/water bottle/appointment at the gym type of exercise. Even 10 minutes of walking around my block was a good start. Some days I could go full out, other days it might be just a little, but above all, frequency was key.
It's a rule I'm trying to implement in my writing. Because I write so much at my day job, it's easy for me to talk myself into thinking that I've "written" for the day and kept my craft sharp.
It's a dangerous assumption. If I leave my novel for too long, subplots get forgotten, I lose track of clues and emotional arcs, and my poor characters hang frozen in time. I once left my heroine stuck halfway through a window when I went on vacation. When I revisited the scene, I had no idea why I put her there. I got her out, but trying to recapture the initial intensity of the scene (as well as the why?) was tough.
It's as hard as trying to get back into some kind of exercise after you've taken time off. Muscles are sore. Motivation is at rock bottom. The entire process is painful.
We all need a break now and then, but I'm trying not to let more than two days go by without digging into the manuscript. So far, it has really helped keep things rolling along. Now, as for the exercise...