I shift between mediums very frequently. Instead of taking a break from writing, I just write in a different medium or in a different way or for a different purpose, so that I don't actually stop writing - I just go to something else. Like going from a big symphony to a piano piece is great and very refreshing, I find. And then going from that to a big concerto, and then having to go out and play.
This is going to sound crazy, but I can hear music in my head. I can imagine a piano or a guitar playing, and I can sort of think out.