I was always taught that if you do something wrong once it's a "mistake"; it you do it wrong twice, it's a "pattern". Now I just make sure to repeat my mistake if I need to. Biggest one was when I spent hours hand-appliqueing on an intricate layered pattern with fusible web. The next morning I realized that my white on white fabric was backwards. The raised polka dots were now on the back of my block. There was no way to fix it because I had used fusible & I didn't have enough fabric, patience or time to re-do the entire block. So I just made 2 more of the remaining blocks with the fabric backwards. You can definitely tell the difference, but I unashamedly put those 3 blocks right down the center of my quilt. It's a baby quilt for family & was one of my first. If anyone has a problem with it -- TOO BAD!
I was going to post a pic of it, but you can't even tell that the fabric is backwards in the photo. It's pretty hard to notice in real life either unless you are within 12" of the quilt. The polka dots do show through, they're just not as shiny as the front and you can't feel them when you touch the quilt. It was a good learning experience for me -- don't try to layout fabric when I'm tired or don't have sufficient light.