I learned to concentrate on where my hand is in guiding that last inch from a Serger instructor. She pointed out that most of us unconsciously pull the fabric to the left, then running off the edge of the fabric. She told us to never put our hand beyond the needle on serging, so then I started watching my hand when coming to the end of my piecing on my sewing machine.....yep, I was pulling the piece slightly to the left. So I started using a stylus to hold my piece at the end so it did not veer off and was held close to the 1/4" marking. It works. Also, I don't sew a 1/4" any more, I use a scant 1/4, my piecing seems to go together better and I am not short fabric when squaring up the block....I would rather trim a block then not have enough and have to unsew lots of pieces.