I am not a fast piecer because I put everything up on the design wall (it is behind my chair) and only take off one item at a time -- and I still will sometimes turn the blocks around.
The worst thing I ever had happen was when I was quilting a quilt using my home sewing machine. I was doing really well, it looked great an I was a happy camper. I had minkee on the back -- when I turned it over, the Minkee had picked up a piece of fabric that I thought was well out of reach of the quilt. It too was well quilted in. I have discovered that reverse quilting is worse than reverse piecing (LOL).