You may have seen the little tomato shaped timers called Pomodoros. The 2016 Writer's Market mentions an app called a Pomodroido. It can be downloaded to your smart phone for writing marathons. Each thirty minute block is called a pomodoro. (I think they should have called them Pomodores.) The article suggest that you take a thirty minute break after four pomodoros. Stand up, stretch and walk around.
I don't have any cute ways to time my writing breaks. In fact, I try to time mine by thought breaks or scene changes. But I break up my writing with prayer. I have prayer lists to pray through while I clear my mind from writing.
I too need to stand up and possibly walk around the block. That is ideal for prayer. When I sit back down to write I am not only refreshed, but I am more in tune with the source of inspiration.
Prayer like writing is something you have to discipline yourself to do. And both of these disciplines work wonderfully together.
