Some Important Things to Remember, an excerpt from Harriet Hargrave & Carrie Hargrave’s Quilter’s Academy Vol. 2 – Sophomore Year, p. 27:
Keep the sewing straight. Most machines tend to pull the fabric to the left as you approach the end of the seam, making the seam allowance narrower and causing a flare to the unit when pressing. Make sure that you enter the fabric at your exact seam allowance and exit at the exact same distance. To do this, sit directly in front of the needle of the machine so that your vision is straight onto the needle and your seam guide system. A stiletto or similar tool, as well as a straight stitch throat plate, can help you hold the edges in place as you get to the end of a seam.