Current productivity theory suggests working in 50 minute segments. The best way to do this is to set a timer so you don’t have to be counting minutes in the back of your head.
Turn off the telephone, email notices, twitter, Facebook, etc. so that during that time segment you can write away unhindered by outside intrusions.
Then take a 10 minute break. I suggest getting up, doing something completely else. In other words, do not remain at the computer to do other tasks like checking email. Get up. Go to another room. Go outside. Doing something physical is a good alternative: do a few exercises, clean the cat litter box, take a brief walk.
Lately, I’ve been using this time to do weed patrol outside. I am restoring an established garden and need to pull the weeds that grow among the other small plants, especially the ground cover so that the garden is weed free. Rain followed by sun produces a new crop.
Whatever you choose as your alternate activity gives your right brain time to process story ideas. You may find that the right word comes to mind or the way to give some extra punch to a scene arrives unbidden.
For example, in a three-hour writing period you will have 30 minutes of “break” time. Ten minutes for each hour.
Without going into the details of brain science you will find that this alternating time use structure will actually improve your writing productivity.
Try using this simple technique for three days. Evaluate it for yourself.