I agree with Frankblt. Breaking your task down to manageable segments will relieve a lot of your stress.

Here's something I came across years ago that your situation reminded me of. It was a web site about keeping your house clean, and the one thing they recommended was setting your kitchen timer for say 15 minutes and doing something around the house. It could be putting in a load of laundry, folding laundry, putting away dishes, dusting the living room or whatever. Just do something for 15 minutes until the timer goes off. It's amazing how effective that can be in keeping you from being overwhelmed by tasks.