I’ve set a digital clock on my computer and phone to ping at the top of every hour. This reminds me to stand up and move.
While I will work through it if I’m in the middle of a writing burst, when the idea is complete, and it is safe to walk away, I will do so for at least five minutes.
Scientific research as shown that sitting for long periods of time is just about as unhealthy as smoking. Writing for 60-90 minutes without moving for only 30 days won’t be the death of you if you are regularly active, but consider a little movement to keep the juices flowing inside your body as well as your mind.
Go make a cup of tea, go drink a glass of water, walk around the room, or to another room and back. Don’t let yourself be distracted by walking into the kitchen or laundry room and seeing something that needs doing. Just move around.
Some writers stand up and do jumping jacks or squats for a few minutes. Many will stretch. Do something upright for just a few minutes once an hour.
You will return to your writing with more energy, a better ability to focus, and possibly a new idea for your story.
You are in the final stretch, so keep stretching.