Read an old Calvin and Hobbes book. Don't only muscle your way through an intellectual barrier. And if you can't get yourself in gear, or give yourself a rest, appoint a self-regulator. Per your instructions, this person will, on schedule, remind or cajole you to ebb and flow. With this arrangement, of course, you now lay the blame for any procrastination on the other's dereliction of duties.
Mother Knows Best.
Learn to break up a big project into smaller, manageable pieces. If highly anxious, start working for five minutes on a complex assignment, then back away. It's amazing, but with this new small window, upon your return to the battlefield, you'll likely feel less intimidated by the overwhelming project dragon. Of course, as a once big procrastinator, I had to learn the hard and humbling way. My writings now appear in Perspectives, the electronic magaine of Mental Health Net.