I think the only way to really mess up a quilt is to simply "NOT" try.
In my case, I feel like my mess ups always have to do with the quilting part of making a quilt. It's a goal, I truly want to feel comfortable and adequate when actually quilting my quilts. Guess I need to practice more. I think I have no less then 5 tops ready to be quilted. I will have to get on that.....soon.