An awful lot of the techniques you would use to help you sew straight lines you can use for sewing curves too. But obviously you will need to turn the fabric whilst checking the masking tap/ magnetic guide/ edge of the foot. This will see you needing to sew a lot more slowly than when you are doing straight lines. Some people find all of this very tricky and I get it.

If you find it too taxing you can always mark your stitch line in at a number of points with an erasable marker, and then draw the actual line in, and then follow this line with your needle when sewing. It is a little more time consuming to prepare but if it saves stress/ swearwords/ frustration/ unpicking then it surely has to be worth it?

A quick way to mark the same measurement over and over is to mark it on a piece of paper or even to put masking tape on your ruler or tape measure, that way you don’t have to keep trying to find the same number on your measuring device. I use bits of paper a lot for this reason!