I used to get mild panic or anxiety attacks when I was worried that I wouldn't be able to complete an assignment on time. The best way I've found for dealing with such stress is to overstress yourself by doing more than you think you can. This is akin to jumping into the deep end of the pool. I've really done this by pushing myself into the 2,500 word per day challenge and then slowly but surely adding more activities for me to do. Training for a race, going on Weight Watchers and editing my books has been a challenge, but I hardly feel those bursts of panic anymore. I feel calm as I power my way through one difficult day after another. Some day, when my hundreds of books are earning me thousands of dollars a week (or day), I may kick back and laugh at the panic attacks I used to have at such trifling work. I will be proud of myself at that time for training myself for that deep end of the productivity pool. Jump in, y'all, the water's just fine :).
In writing news, I worked on Why I'm Not Famous Yet and wrote a blog post on getting your to-do list clear called last things first.