This is important because you need to feel that you have stopped, not simply refuelled. All workers need a rest and a chance to think - especially crucial for a writer. During pauses, you can regather your tangled ideas and sort them out, ready to move on afterwards. Give your poor brain a five-minute pause.
Remember to do it at the appropriate moment, not when you're in mid-flow. Savour the satisfaction of relaxing at just the right point. However, leave it at a place where you can easily continue, not at a finished and polished place. It is hard to pick up without one little loose thread to seize.