It’s easy for a writer to become too introverted and staring at the same four walls can be detrimental to the whole creative process. If you start to feel stale then take yourself out for the day and visit somewhere new but don’t switch off your creative thoughts, instead soak up your surroundings like a sponge and recharge your batteries.
Make a mental note of the people that you see, events that occur and absorb the scenery. You can even try creating little fictional plots as you enjoy your day. Any ideas that you get may well come in useful for when back at your desk but most of all you will feel mentally refreshed and ready to start writing again.