Stop worrying! Do the best you can without worrying about being perfect. Have fun or why do it.
I think Clsurz just had a post in the last few days here about her experience with a swap. My sometimers kicked in and I can't remember the title but try to look for it and read it before you start.
Found it: I Will Never Again
http://www.quiltingboard.com/t-155913-1.htm