At times, we all have a 'monkey mind' that doesn't seem to want to concentrate on the writing we need to do. In fact, sometimes the closer the deadline, the more active the monkey mind!
New Scientist Magazine rides to the rescue with these suggestions:
First, raise your arousal level, either with coffee, or by making sure you've had a good night's rest, don't eat sugary foods, and get plenty of exercise so you'll feel fresh.
Second, reduce distractions. Turn off the phone, put a 'do not disturb' sign on your desk, or go somewhere where you won't be disturbed. Studies suggest that after being interrupted by a phone call, it will take you a quarter of an hour to get back into a deep state of concentration.
Third, listen to soothing music that blocks out random background noise.
Fourth, practice catching yourself when your thoughts start to wander, and give yourself the command, "Stop! Be here now!" and get back to work.
One I'd add: stop compulsively checking your email every fifteen minutes (hmm, I wonder why I thought of that one...).