I have made soooo many mistakes that I can't really define one exactly, but I remember cutting out 8" squares for the background for my applique Snowmen. After I cut 36 squares out, I reread the instructions and realized they were suppose to be 9". The Snowmen had very many pieces to each one and I had the hardest time making each piece small enough to look right on the smaller block. It made the entire quilt a nightmare. I had to try all different sizes for each piece of the snowman and the trees and birds and fence and house in each block. I know to read the instructions twice and cut once, but I had to learn the hard way. What was your biggest mistake?