When I was in a rush yesterday to finish up assembling my last set (row) of blocks. I was sewing them one after the other, adding each new piece as I restarted on the pile. After sewing the last block, I saw that I had one piece left over that didn't have a block to go with it. I knew I had cut the right amount of pieces that I needed. But I couldn't wrap my head around it and it confused me for a moment until I ironed my blocks and realized that - no I didn't cut an extra piece, but that I had sewn two blocks layered together. Luckily I was able to get the two sewn together apart without destroying them and then sheepishly finished sewing that block again and adding the last piece to the last block to finish!