Especially when you are trying to sew speedily. I glanced at the Star Wars fabric I had cut out for a tote bag, noticed that 'Star Wars' was right side up and commenced to sewing. Except, Except, Except, when I was done sewing I noticed that the SHIPS WERE UPSIDE DOWN! It turns out that on this fabric, 'Star Wars' is always right side up. :Le Sigh: So now it is in the shop as a 'One of a Kind Upside Down Star Wars Bag'.
I think it is still an awesome bag, and hey, if it doesn't sell in the shop, I will have a funny story to carry stuff around in.